| 1. |
- Ahlin, Lars, et al.
(författare)
-
Principles of Wireless Communications
- 2006
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Bok (refereegranskat)abstract
- This textbook provides the reader with a basic understanding of the design and analysis of wireless and mobile communication systems. It deals with the most important techniques, models and tools used today in the design of mobile wireless links and gives an introduction to the design of wireless networks. Topics covered include: fundamentals of radio propagation and antennas; transmission schemes, including modulation, coding and equalising schemes for broadband wireless communications; diversity systems; wireless data transmission; introduction to Wireless Network design and resource management. The fundamentals are illustrated by examples from state-of-the-art technologies such as OFDM, WCDMA, WLANs and others. The book contains a significant number of worked examples and more than 160 problems with answers. It is intended for use in a first graduate course in wireless communications and the reader should be familiar with the fundamentals of probability and communication theory.
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| 2. |
- Ahsin, Tafzeel Ur Rehman, et al.
(författare)
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Constellation Selection in Network Coded Distributive Antenna System
- 2009
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Ingår i: GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference. - : IEEE. - 9781424441471 ; , s. 342-346
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Konferensbidrag (refereegranskat)abstract
- Relays can improve wireless links by providing an extra path to the direct path which together form a virtual multiple antenna system. Network Coded-Distributive Antenna System (NC-DAS) and Plain-Distributive Antenna System (P-DAS) are examples of realizations of such scenario. Although the asymptotic diversity gain for both the schemes is comparable, the network coded scheme can further take advantage of the redundancy and the extra dimension provided by the relay link. This extra signal dimension can be very useful when multilevel modulation is employed as it gives the possibility for a better spread of the modulation signal points within the augmented signal space. This article presents a simple and effective Constellation Selection (CS) scheme for all the three links within the NC-DAS system. This selection procedure improves the bit error probability in both AWGN and Rayleigh fading channels. Two different detections schemes are considered in the paper. Joint detection where the both users are decoded simultaneously and detection with successive cancelation where the strongest user is detected first followed by cancelation and maximum ratio combining. Analytical expressions for the error probability supported by simulation results are presented. The obtained results show that constellation selection provides good performance gain as compared to the case of same constellation.
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| 3. |
- Ahsin, Tafzeel Ur Rehman, et al.
(författare)
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Energy Efficiency using Cooperative Relaying
- 2011
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Ingår i: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC). - New York : IEEE. - 9781457713484 ; , s. 1698-1702
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Konferensbidrag (refereegranskat)abstract
- The rising demand for the high data rates in the future cellular systems, is directly linked with the power consumption at the transmitting nodes. Due to the various economical and environmental factors, it is becoming difficult to maintain the current rate of power consumption per unit of data, for the upcoming generations of the cellular systems. This has shifted the focus of many researchers towards the energy efficiency aspect of the cellular systems and power consumption has become an important design parameter in the recent works. In this article, we propose the use of cooperative communications using low cost fixed relays, in order to reduce the energy consumption at the transmitting nodes for a given quality of service requirement. It has been investigated that, how different factors, such as cell radius, relay position, number of relays and target data rate effects the area energy consumption for the different relaying schemes. It has been shown that, the cooperative relaying schemes along with adaptive resource allocation provides minimum energy consumption along with the better coverage as compared to the non adaptive cooperative relaying schemes.
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| 4. |
- Ahsin, Tafzeel ur Rehman, 1979-
(författare)
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Link Reliability in Cooperative Relaying Using Network Coding
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Demand for high data rates is increasing rapidly for future wireless systems.This trend is due to the increase in the number of mobile subscribers that need bandwidth hungry multimedia applications anywhere, anytime. Fourth generation cellular systems like IMT-advanced are being developed to meet these requirements. The unreliable nature of the wireless medium is one of the main hinderance in providing high data rates. Cooperative communication in cellular networks is emerging as a new paradigm to deal with the channel impairments. User cooperation via fixed relays in cellular systems form multiple access relay channels (MARCs) and provide an effective and cost efficient solution to achieve spatial diversity gains. Network resources can be utilized efficiently by using network coding at cooperating nodes. A lot of research work has focused on highlighting the gains achieved by using network coding in MARCs. However, there are certain areas that are not fully explored yet. For instance, the kind of the detection scheme used at the base station receiver and its impact on the link performance has not been addressed. In most cases, the outage probability has been used as a performance measure of MARCs. However, it is well known that the outage probability gives information about the signal availability, but it does not give the complete picture about the reliability of the link and the achieved quality of service. This thesis work looks at the link performance, in terms of symbol error probability, of multiple access relay channels that employ network coding at the relay node. Different types of detection schemes are considered and their performance is compared under different link conditions. Analytical expressions for the average symbol error probability of the cooperating users are derived. Focusing on the uplink of cellular systems, certain rules are devised on how to group users at relay node to ensure mutual benefit for the cooperating users. As a way of improving the link performance of multiple access relay channels and their robustness, the thesis considers constellation selection for the different branches. This method takes advantage of the redundancy between the transmitted symbols created by network coding and the augmented signal space obtained at the base station receiver. The obtained results show that, with a proper selection of the constellation sets, the link performance of MARCs can be improved. The thesis further looks at the interaction between the channel coding schemes of the cooperating users and network coding. It is shown that joint channel-network coding in MARCs can be seen as a product code. This new representation provides considerable flexibility in selecting efficient decoding algorithms at the base station receiver and gives the possibility to use more powerful network coding schemes for MARCs.
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| 5. |
- Ahsin, Tafzeel ur Rehman, et al.
(författare)
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Network coding based on product codes in cooperative relaying
- 2010
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Ingår i: IEEE Wireless Communications and Networking Conference 2010, WCNC 2010. - 9781424463985
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Konferensbidrag (refereegranskat)abstract
- Employing network coding at the relay in cooperative relay system can improve the system throughput. However, XOR based network coding does not provide a strong error correction capability that can be used at the base station (receiver) in decoding the information of the cooperating users. Instead a block code can be used to combine the received user packets at the relay station where only the extra redundancy of the block code are forwarded by the relay station. With this structure a better error correction capability is embedded to the network coding scheme providing a better help to the receiver when decoding the user information. Combining this network coding structure with the individual block codes of the users, an overall product code can be obtained which gives the possibility of generating more powerful overall codes and increases the correction capability of the decoding process at the receiver. The obtained results show that the proposed scheme outperforms the conventional XOR based network coding scheme and gives the possibility of combining more users in the cooperation process.
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| 6. |
- al-Askary, Omar, et al.
(författare)
-
Effect of error in CSI on the capacity of Rayleigh fading channels with QAM signalling and the design of robust signal constellations
- 2007
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Ingår i: IET Communications. - : Institution of Engineering and Technology (IET). - 1751-8628 .- 1751-8636. ; 1:6, s. 1118-1125
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Tidskriftsartikel (refereegranskat)abstract
- The effects of channel estimation errors on the channel capacity of a discrete time, discrete input, infinite output Rayleigh fading channel are investigated. The case of conventional modulation methods such as phase shift keying (PSK) and quatrature amplitude modulation (QAM) is investigated at first where it was observed that the capacity degrades rapidly with increasing channel estimation errors. The effect of error in the channel estimation is similar to the effect of higher noise in the channel that depends on the transmitted signal. A genetic algorithm is used to optimise the signal constellation in order to maximise the capacity for a given finite number of signal points. The aim of trying to maximise the capacity is to estimate the remaining gap in performance between a traditional modulation scheme such as QAM and the best possible constellation that is optimised for the channel. The constellations obtained from the genetic algorithm are, in general, not directly implementable. A method to design practical robust signal constellations that overcome the effect of channel state information (CSI) error is presented. The robust signal constellations obtained show a performance that is very close to the optimal constellations. In this work, the probability distribution of the error in CSI is assumed to be known.
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| 7. |
- Awan, Zohaib Hassan, et al.
(författare)
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Improved Beamforming for Radio Links with Multi-Level Linearly Modulated Signals
- 2009
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Ingår i: 2009 IEEE WIRELESS COMMUNICATIONS & NETWORKING CONFERENCE. - 9781424429479 ; , s. 913-917
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Konferensbidrag (refereegranskat)abstract
- Multiple constellations has been proposed recently as a way of improving the system performance when used in conjunction with Orthogonal Transmit Diversity (OTD) for high level linear modulation schemes. This paper considers the use of multiple constellations in Multiple Input Multiple Output (MIMO) antenna systems. The premise is that the same modulation scheme is used with different bits to symbols mapping for each branch. This improved beamforming results in better performance as compared to MIMO-MRC where the same bits to symbols mapping is used on all branches. Analytical expression for Symbol Error Probability (SEP) is derived. The results obtained show that the new proposed improved beamforming scheme outperforms conventional MIMO-MRC with a performance dividend that increases with the linear modulation level.
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| 8. |
- Ben Slimane, Slimane, et al.
(författare)
-
A doubly stochastic Poisson model for self-similar traffic
- 1995
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Ingår i: IEEE International Conference on Communications. ; , s. 456-460
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a data traffic model capable of describing the long-range dependence and self-similar burstiness structure found in measurement studies of packet data traffic. The model introduced is based on doubly stochastic Poisson processes. The intensity of arrivals is modeled as a continuous stochastic process. This process satisfies most of the properties found in the measurement studies, namely long-range dependence and self-similarity. The generality and simplicity of this model makes it attractive in data traffic modeling
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| 9. |
- Ben Slimane, Slimane
(författare)
-
A low complexity antenna diversity receiver for OFDM based systems
- 2001
-
Ingår i: IEEE International Conference on Communications. ; , s. 1147-1151
-
Konferensbidrag (refereegranskat)abstract
- A low complexity antenna diversity architecture with a new combining technique suitable for orthogonal frequency division (OFDM) based systems is introduced in this paper. For a two branch antenna diversity, this structure requires only one FFT at the receiver and allows optimum maximum ratio combining. For systems with a higher number of antennas, the number of required FFTs when using such technique is reduced by half as compared to the conventional case where a different FFT is used for each receive antenna. As a result a considerable reduction in processing complexity is obtained especially for systems with high number of subcarriers. This method can also be seen as a way of increasing the number of antennas in OFDM transceivers without any major complexity increase. Thus, a considerable increase in diversity gain can be achieved
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| 10. |
- Ben Slimane, Slimane, et al.
(författare)
-
An Improved Cancellation Multiuser Detector for Narrowband Signals
- 2005
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Ingår i: VTC 2005-Spring. - New York : IEEE. - 0780388879 ; , s. 973-977
-
Konferensbidrag (refereegranskat)abstract
- This paper examines the possibility of reducing error propagation in the successive interference cancellation multiuser detector (SIC-MUD) for a narrowband system. A simple sequence estimation algorithm is employed, working on a symbol by symbol user basis, not affecting the operation of FEC decoding if present. Operating along the stages of the SIC-MUD scheme, this algorithm has a complexity that increases only linearly with the number of users and thus can be used for a larger number of users, as against the optimum joint detection-MUD (JD-MUD), whose complexity increases exponentially with the number of users. Investigation is carried out for both AWGN and Rayleigh fading channels. The obtained results show that the Improved SIC-MUD scheme reduces the error propagation considerably and, with its low complexity, can be a good alternative for the JD-MUD scheme.
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| 11. |
- Ben Slimane, Slimane
(författare)
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An Improved PSK Scheme for Fading Channels
- 1996
-
Ingår i: Global Telecommunications Conference, 1996. GLOBECOM '96. 'Communications: The Key to Global Prosperity. - : IEEE. - 0780333365 ; , s. 1276-1280
-
Konferensbidrag (refereegranskat)abstract
- The performance of uncoded PSK schemes over fading channels is only inversely proportional to the signal-to-noise ratio, which is not very reliable for digital communication applications. Improving their performance has been approached by means of coded modulation schemes where code redundancy combined with interleaving introduces some degree of diversity that depends on the complexity of the code. This paper proposes an alternative method of improving the performance of PSK schemes over fading channels by looking at the reference scheme first. It is shown that by using interleaving combined with a proper signal constellations and still using symbol-by-symbol detection, a higher diversity is obtained and the performance of uncoded PSK schemes over fading channels is considerably improved. With this simple modification, the obtained performance is comparable to that of the best 4-state trellis coded modulation (TCM) 8PSK schemes reported in the literature. By optimizing the reference scheme first, it is shown that this technique optimizes the performance of Ungerboeck's trellis coded 8PSK schemes over fading channels. Infact, without altering their performance over the additive white Gaussian noise channel, significant coding gain over fading channels is achieved.
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| 12. |
- Ben Slimane, Slimane
(författare)
-
An Improved PSK Scheme for Fading Channels
- 1998
-
Ingår i: IEEE Transactions on Vehicular Technology. - New York : IEEE. - 0018-9545 .- 1939-9359. ; 47:2, s. 703-710
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of uncoded phase-shift-keying (PSK) schemes over fading channels is only inversely proportional to the signal-to-noise ratio, which is not very reliable for digital communication applications. Improving their performance has been approached by means of coded modulation schemes, where code redundancy combined with interleaving introduces some degree of diversity that depends on the complexity of the code. This paper proposes an alternative way in improving the performance of PSK schemes over fading channels by looking at the reference scheme first. It is shown that by using interleaving combined with a proper signal constellations and still using symbol-by-symbol detection, a higher diversity is obtained and the performance of uncoded PSK schemes over fading channels is considerably improved. With this simple modification, the obtained performance is comparable to that of the best four-state trellis-coded-modulation (TCM) 8PSK schemes reported in the literature. By optimizing the reference scheme first, it is shown that this technique optimizes the performance of Ungerboeck's trellis-coded 8PSK schemes over fading channThe performance of uncoded phase-shift-keying (PSK) schemes over fading channels is only inversely proportional to the signal-to-noise ratio, which is not very reliable for digital communication applications. Improving their performance has been approached by means of coded modulation schemes, where code redundancy combined with interleaving introduces some degree of diversity that depends on the complexity of the code. This paper proposes an alternative way in improving the performance of PSK schemes over fading channels by looking at the reference scheme first. It is shown that by using interleaving combined with a proper signal constellations and still using symbol-by-symbol detection, a higher diversity is obtained and the performance of uncoded PSK schemes over fading channels is considerably improved. With this simple modification, the obtained performance is comparable to that of the best four-state trellis-coded-modulation (TCM) 8PSK schemes reported in the literature. By optimizing the reference scheme first, it is shown that this technique optimizes the performance of Ungerboeck's trellis-coded 8PSK schemes over fading channels. In fact, without altering their performance over the additive white Gaussian noise (AWGN) channel, significant coding gain over fading channels is achieved.els. In fact, without altering their performance over the additive white Gaussian noise (AWGN) channel, significant coding gain over fading channels is achieved
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| 13. |
- Ben Slimane, Slimane
(författare)
-
Approximation to the Symmetric Capacity of Rayleigh Fading Channels with Multi-Level Signals
- 2006
-
Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 0:3, s. 129-131
-
Tidskriftsartikel (refereegranskat)abstract
- A simple approximation for the symmetric capacity of Rayleigh fading channels with finite input alphabet and ideal channel state information is proposed in this letter. This approximation is quite tight over all SNR ranges and can be considered as a good alternative for estimating the symmetric channel capacity for both AWGN and Rayleigh fading channels.
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| 14. |
- Ben Slimane, Slimane
(författare)
-
Bandwidth efficiency of MC-CDMA Systems
- 1999
-
Ingår i: Electronics Letters. - New York : IEEE. - 0013-5194 .- 1350-911X. ; 35:21, s. 1797-1798
-
Tidskriftsartikel (refereegranskat)abstract
- The bandwidth efiiciency of MGCDMA signals is evaluated and Compared to that of DS-CDMA signals. For the same available bandwidth, the achievable processing gain of the two systems with and without Sdtetering is evaluated and then Compared.
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| 15. |
- Ben Slimane, Slimane
(författare)
-
Bounds on the Distribution of a Sum of Independent Lognormal Random Variables
- 2001
-
Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 49:6, s. 975-978
-
Tidskriftsartikel (refereegranskat)abstract
- The distribution function of a sum of lognormal random variables (RVs) appears in several communication problems. Approximations are usually used for such distribution as no closed form nor bounds exist. Bounds can be very useful in assessing the performance of any given system. In this letter, we derive upper and lower bounds on the distribution function of a sum of independent lognormal RVs. These bounds are given in a closed form and can be used in studying the performance of cellular radio and broadcasting systems.
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| 16. |
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| 17. |
- Ben Slimane, Slimane
(författare)
-
Channel estimation for HIPERLAN/2 with transmitter diversity
- 2002
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Ingår i: 2002 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-5, CONFERENCE PROCEEDINGS. ; , s. 26-30
-
Konferensbidrag (refereegranskat)abstract
- In this paper we propose a channel estimation technique for OFDM based systems, such as HIPERLAN/2 and IEEE 802.11a, with transmitter diversity. The proposed technique estimates all channel frequency responses, corresponding to each transmitter and receiver antenna pair, required for space-time processing In this OFDM based system. This technique is able to extract the channel state Information for two transmitter antennas using the same preamble as defined in the standard of HIPERLAN/2. The feasibility of this channel estimation method Is made possible by exploiting the structure of the OFDM modulation scheme. The results showed that the accuracy provided by this proposed method is comparable to that obtained when a single transmitter antenna is used.
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| 18. |
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| 19. |
- Ben Slimane, Slimane, et al.
(författare)
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Coded quadrature pulse-overlapping modulation techniques for personal communications
- 1992
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Ingår i: 1st International Conference on Universal Personal Communications, 1992. ICUPC '92 Proceedings. ; , s. 11-03/1-11-03/5
-
Konferensbidrag (refereegranskat)abstract
- Hard-limited quadrature pulse-overlapping modulation (QPOM) techniques have a constant envelope, good spectral properties and good performance especially in fading channels. These modulation techniques are suitable to applications using nonlinear or saturated power amplifiers to obtain high power and bandwidth efficiencies. A technique to combine convolutional codes and QPOM schemes to further improve its performance in fading channels is introduced and evaluated. At first, the QPOM scheme is decomposed into an encoder followed by a memoryless modulator. Then, the binary convolutional encoder is concatenated to the QPOM encoder and considered as one entity to be optimized. Performance of the coded QPOM scheme is analyzed and compared to uncoded QPOM and coded QPSK schemes
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| 20. |
- Ben Slimane, Slimane
(författare)
-
Combined transmitter diversity and multi-level modulation techniques
- 2006
-
Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 39:2, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- Orthogonal transmitter diversity such as frequency diversity and time diversity is quite simple to implement and, with optimum signal combining, can take full advantage of fading multipath channels. However, such a scheme has a bandwidth efficiency that decreases inversely with the number of diversity branches making it less attractive in wireless communications applications. This paper considers combined orthogonal transmitter diversity and multi-level linear modulation techniques. The idea is to view the signal constellations of the modulation scheme in an augmented signal space formed by the modulation signal dimension and the number of branches of the transmitter diversity scheme. This augmented signal space provides a good spread for the modulation signal points and can be quite efficient for high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance on both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity.
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| 21. |
- Ben Slimane, Slimane
(författare)
-
Combined Transmitter Diversity and Multi-Level Modulation Techniques
- 2005
-
Konferensbidrag (refereegranskat)abstract
- Orthogonal transmitter diversity such as frequency diversity and time diversity is quite simple to implementand, with optimum signal combining, can take full advantage of fading multipath channels. However, such a scheme has a bandwidth efficiency that decreases inversely with the number of diversity branches making it less attractive in wireless communications applications. This paper considers combined orthogonal transmitter diversity and multi-level linear modulation techniques. The idea is to view the signal constellations of the modulation scheme in an augmented signal space formed by the modulation signal dimension and the number of branches of the transmitter diversityscheme. This augmented signal space provides a good spread for the modulation signal points and can be quite efficientfor high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance in both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity.
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| 22. |
- Ben Slimane, Slimane, et al.
(författare)
-
Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity
- 2008
-
Ingår i: 2008 IEEE International Conference On Communications, Proceedings. - 9781424420742 ; , s. 3553-3557
-
Konferensbidrag (refereegranskat)abstract
- Cooperative relaying has recently been recognized as an alternative to MIMO in a typical multi cellular environment Inserting random delays at the non-regenerative fixed relays, further improve the system performance. However, random delay results in limited performance gain from multipath diversity. In this paper, two promising delay optimization schemes are introduced for a multi cellular OFDM system with cooperative relaying with stationary multiple users and fixed relays. Both of the schemes basically aim to take the most advantages of the potential frequency selectivity by inserting pre-determined delays at the relays, in order to further improve the system performance (coverage and throughput). Evaluation results for different multipath fading environments show that the system performance with delay optimization increases tremendously compared with the case of random delay.
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| 23. |
- Ben Slimane, Slimane, et al.
(författare)
-
Delay Optimization in Cooperative Relaying with Cyclic Delay Diversity
- 2008
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Ingår i: EURASIP Journal on Advances in Signal Processing. - : Springer Science and Business Media LLC. - 1687-6172 .- 1687-6180. ; , s. 736818-
-
Tidskriftsartikel (refereegranskat)abstract
- Cooperative relaying has recently been recognized as an alternative to MIMO in a typical multicellularenvironment. Inserting random delays at the nonregenerative fixed relays further improve the system performance.However, random delays result in limited performance gain from multipath diversity. In this paper, two promisingdelay optimization schemes are introduced for a multicellular OFDM system with cooperative relaying withstationary multiple users and fixed relays. Both of the schemes basically aim to take the most advantages ofthe potential frequency selectivity by inserting predetermined delays at the relays, in order to further improve thesystem performance (coverage and throughput). Evaluation results for different multipath fading environments showthat the system performance with delay optimization increases tremendously compared with the case of randomdelay.
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| 24. |
- Ben Slimane, Slimane, et al.
(författare)
-
IJF-OQPSK modulation schemes with MLSE receivers for portable/mobile communications
- 1992
-
Konferensbidrag (refereegranskat)abstract
- A receiver structure for constant enveloped IJF-OQPSK modulation under fading channel conditions is introduced. Its performance in AWGN and Rayleigh fading channels was analyzed and verified by computer simulations. Results show the relation between the performance of the system and the memory introduced by the double-interval overlapping pulse shape. By properly using this memory, it is possible to achieve superior performance compared to conventional schemes. Even though no coding has been used, comparable results to coded schemes was obtained with no extra redundancy. Therefore, the complexity caused by multilevel modulation can be avoided, and transmission of signals with compact spectrum and good performance is possible. The constant envelope, compact spectrum, superior performance in fading channels and low complexity make the hardlimited IJF-OQPSK scheme a good choice for portable/mobile communications, to achieve low cost, small size, and high power and bandwidth efficiencies
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| 25. |
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| 26. |
- Ben Slimane, Slimane
(författare)
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MC-CDMA with Quadrature Spreading for Wireless Communication Systems
- 1998
-
Ingår i: European transactions on telecommunications. - Milano : Assoc Elettrotecnica Ed Elettronica Italiana. - 1124-318X .- 2161-3915 .- 1541-8251. ; 9:4, s. 371-378
-
Tidskriftsartikel (refereegranskat)abstract
- MultiCarrier CDMA (MCCDMA) systems using the Orthogonal Frequency Division Division Multiple Access (OFDM) technique resolve the frequency se lectivity in multipath fading channels and have good spectral properties. The addition of a spread spectrum component to the OFDM introduces a frequency diversity gain that can combat deep multipath fading situations. In this paper a MCCDMA system operating over frequency selective, slowly fading channels is considered and its performance is studied analytically and by computer simulations. We consider the downlink of a cellular radio system where for each user a BPSK modulation and a quadrature (complex) spreading code is used. The spreading codes are arranged in a way that reduces the effect of the multipath fading channel and restores some of the orthogonality losses between users. The obtained results show considerable performance improvement compared to conventional OFDM and to MCCDMA that uses single spreading codes. The effect of frequency offsets on the system performance is also addressed in this paper. Its superior performance and low complexity receiver make MCCDMA with quadrature spreading codes suitable for future wireless communication systems to achieve the requirements of high quality services, high speed, and low costreceiver.
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| 27. |
- Ben Slimane, Slimane
(författare)
-
MC-CDMA with Quadrature Spreading over Frequency Selective Fading Channels
- 1997
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Ingår i: Conference Record / IEEE Global Telecommunications Conference. - New York : IEEE. - 0780341988 ; , s. 315-319
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Konferensbidrag (refereegranskat)abstract
- MultiCarrier CDMA (MCCDMA) schemes resolve the frequency selectivity in multipath fading channels and have good spectral properties. Spreading the information over many subcarriers adds flexibility to the system and a redundancy between subcarriers that can be combined nicely with the derived frequency diversity out from the fading channel. In this paper the performance of a MCCDMA scheme over frequency selective, slowly fading channels is studied analytically and by computer simulations. The MCCDMA system uses a BPSK modulation, quadrature (complex) spreading codes, and a simple correlator receiver. Quadrature spread ing codes are used to reduce the effect of the multipath fading channel and restore some of the orthogonality losses be tween users. The obtained results show considerable performance improvement compared to conventional Orthogonal Frequency Division Multiplexing (OFDM) scheme and MCCDMA schemes that use nonquadrature spreading. The effect of frequency offsets on the system performance is also addressed in this paper.
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| 28. |
- Ben Slimane, Slimane, et al.
(författare)
-
Multi-carrier CDMA systems using bridge functions
- 2000
-
Ingår i: Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. 2000 IEEE 51st. - New York : IEEE. - 0780357183 ; , s. 1928-1932
-
Konferensbidrag (refereegranskat)abstract
- Multi-carrier CDMA systems appear to be a good candidate for high speed wireless data transmission. These systems avoid time domain equalization and have the capability of achieving high diversity gains over frequency selective fading channels. Orthogonal Walsh-Hadamard spreading waveforms have been commonly considered for these systems. However, reliable system performance over frequency selective fading channels requires complicated detector structures with a complexity that increases with the length of the spreading code. In this paper a multi-carrier CDMA system using the Bridge functions as spreading waveforms is considered and its performance over frequency selective fading channels is evaluated. The bridge functions are three valued orthogonal functions which take the values +1, 0, and -1. Such a structure adds flexibility to the multi-carrier CDMA where the number of zeros in the spreading code can be used to decide on the frequency separation between the modulated subcarriers and thus avoiding the need for frequency interleaving. Another benefit is the possibility to use more powerful detectors at the receiver. In fact, this combined system can be seen as a generalization to multi-carrier CDMA where the bridge functions play the role of bridging between the regular OFDM with no spreading and multi-carrier CDMA with Walsh-Hadamard functions.
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| 29. |
- Ben Slimane, Slimane
(författare)
-
OFDM Schemes with Non-Overlapping Time Waveforms
- 1998
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Ingår i: Vehicular Technology Conference, 1998. VTC 98. 48th IEEE. - New York : IEEE. - 0780343204 ; , s. 2067-2071
-
Konferensbidrag (refereegranskat)abstract
- For orthogonal frequency division multiplexing (OFDM) schemes, the time waveform plays a major role not only in shaping the spectrum of the transmitted signal but also in separating the signal subcarriers at the receiver. The selection of such waveform is then very important and can make a big difference in spectrum utilization and system performance. The difficulty in using pulse shaping with OFDM appears in the detector design since smooth time waveforms destroy the orthogonality between subcarriers and introduce inter-channel interference (ICI). This paper investigates the use of non-overlapping signal waveforms for OFDM schemes. It is shown that pulse shaping for such schemes can be equivalently achieved using a discrete shaping matrix. Such a shaping structure is very suitable for digital implementation and can be combined with OFDM schemes without affecting their IDFT/DFT operators. It therefore makes the use of guard time interval (cyclic prefix) for OFDM schemes possible with any kind of non-overlapping shaping waveform.
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| 30. |
- Ben Slimane, Slimane, et al.
(författare)
-
On the Capacity of CDMA with Linear Successive Interference Cancellation
- 2003
-
Ingår i: European transactions on telecommunications. - : Wiley. - 1124-318X .- 2161-3915 .- 1541-8251. ; 14:6, s. 501-513
-
Tidskriftsartikel (refereegranskat)abstract
- Combined power control and interference cancellation in CDMA systems can be a very efficient resourcemanagement tool. While conventional power control tries to maintain equal received power or balancedsignal-to-interference ratio (SIR), successive interference cancellation (SIC) in multi-user detection (MUD)relies more on the disparities between the powers of the different users. The combination can save morepower into the system and thus a room for a better capacity. This paper investigates the interaction between power control and linear SIC in a single-rate CDMAsystem and its impact on the system capacity. The obtained results show that interference cancellation canimprove the capacity of CDMA and relax power control requirements. The full integration of power controland linear SIC detection is shown to provide excellent resource management in CDMA systems. Limitedinterference cancellation can be a good solution for CDMA systems as it provides considerable capacitygain with reduced complexity. An upper bound on the system capacity as a function of the cancellationparameters used along the different stages of the SIC detector is derived. Investigation of the optimumdecoding order is also provided in this paper.
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| 31. |
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| 32. |
- Ben Slimane, Slimane
(författare)
-
Partial Equalization of Multi-Carrier CDMA in Frequency Selective Fading Channels
- 2000
-
Ingår i: IEEE International Conference on Communications. - New York : IEEE. - 0780362837 ; , s. 26-30
-
Konferensbidrag (refereegranskat)abstract
- We consider the detection of multi-carrier-code division multiple access (MC-CDMA) signals in frequency selective fading channels using partial channel equalization. By partially compensating for the fading channel amplitude we can reduce the multi-user interference without considerably enhancing the additive noise level. As a result the MC-CDMA scheme can exploit the frequency diversity of the channel without the need for very complicated detection schemes. The obtained results show considerable performance improvement as compared to that of conventional detection schemes that try to fully compensate for the channel variations. In fact, the performance of this partial channel compensation based detector is not far from that of the optimum minimum mean square error (MMSE) combining detector.
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| 33. |
- Ben Slimane, Slimane
(författare)
-
Peak-to-average power ratio reduction of OFDM signals using broadband pulse shaping
- 2002
-
Ingår i: IEEE 56TH VEHICULAR TECHNOLOGY CONFERENCE, VTC FALL 2002, VOLS 1-4, PROCEEDINGS. - 0780374673 ; , s. 889-893
-
Konferensbidrag (refereegranskat)abstract
- Orthogonal Frequency Division Multiplexing (OFDM) techniques allow the transmission of high data rates over broadband radio channels subject to multipath fading without the need for powerful channel equalization. However, they are very sensitive to nonlinear effects due to the high Peak-to-Average Power Ratio (PAPR) owned by the transmitted signal. This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is very effective and flexible. The method avoids the use of extra Inverse Fast Fourier Transformations (IFFTs) as was done in some previously published techniques but instead is based on a proper selection of the time waveforms of the different sub-carriers of the OFDM modulation scheme. Thus, its implementation complexity is much low in comparison to the previous published methods. A closed form relation between the maximum PAPR and the used pulse shaping waveform is derived. The obtained results show that with broadband pulse shaping, the PAPR of OFDM modulated signals can be made very close to that of single carrier signals. The improved statistics of the PAPR in the transmitted signal is demonstrated through numerical results for some sets of time waveforms. The significant improvement in PAPR given by the present technique permits to reduce the complexity and cost of the transmitter significantly. In that, pulse shaping can be used not only to shape the spectrum of the transmitted signal but also to reduce its PAPR.
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| 34. |
- Ben Slimane, Slimane
(författare)
-
Peak-to-Average Power Ratio Reduction of OFDM Signals using Pulse Shaping
- 2000
-
Ingår i: Global Telecommunications Conference, 2000. GLOBECOM '00. IEEE. - New York : IEEE. ; , s. 1412-1416
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is very effective and avoids the use of extra inverse fast Fourier transformations (IFFTs) as was done in some previously published techniques but instead is based on a proper selection of the time-limited waveforms of the different subcarriers. Thus, its implementation complexity is also much lower in comparison to the previous published methods. This technique is also very flexible and it can be used for OFDM and discrete multi-tone (DMT) transmissions. The improved statistics of the PAPR in the transmitted signal is demonstrated through numerical results for some sets of time waveforms. The significant improvement in PAPR given by the present technique permits to reduce the complexity and cost of the transmitter significantly.
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| 35. |
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| 36. |
- Ben Slimane, Slimane, et al.
(författare)
-
Performance of 16-QPOM signals on a fading mobile satellite channel
- 1993
-
Ingår i: Proceedings of the IEEE 1993 Pacific Rim Conference on Communications, Computers and Signal Processing. ; , s. 674-677
-
Konferensbidrag (refereegranskat)abstract
- The authors present a maximum likelihood sequence estimation (MLSE) receiver structure for both linear and hard-limited 16-quadrature pulse overlapping modulation (QPOM) schemes. Using this structure, the performance of these schemes over shadowed Rician fading channels is studied. The structure of linear 16-QPOM schemes allowed the use of independent decoding for in-phase and quadrature components of the transmitted signal, thus reducing considerably the complexity of the MLSE receiver. The hard-limited 16-QPOM scheme used two hard-limited QPOM schemes in parallel. It is shown that an optimum MLSE receiver for this type of signal needs to consider both in-phase and quadrature components at the same time. Using the MLSE receiver, both schemes outperform conventional coherent 16-quadrature amplitude modulation (QAM)
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| 37. |
- Ben Slimane, Slimane, et al.
(författare)
-
Performance of 16-QPOM signals on a fading mobile satellite channel
- 1993
-
Ingår i: Proceedings of the IEEE Global Telecommunications Conference. - : IEEE. ; , s. 1787-1791
-
Konferensbidrag (refereegranskat)abstract
- Presents the bit error probability of 16-QPOM schemes over mobile satellite shadowed Rician fading channels. An upper bound on the pairwise error probability is derived, and then combined with the transfer function bounding technique. The derived upper bound is given in a closed form without the need of any numerical integration. This upper bound is then used to evaluate the performance of both linear and hard-limited 16-QPOM signals. Simulation results are also performed to verify the analytical results
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| 38. |
- Ben Slimane, Slimane
(författare)
-
Performance of OFDM Systems with Time-Limited Waveforms over Multipath Radio Channels
- 1998
-
Ingår i: Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE. - New York : IEEE. - 0780349849 ; , s. 962-967
-
Konferensbidrag (refereegranskat)abstract
- Pulse shaping can effectively reduce the sensitivity of orthogonal frequency division multiplexing (OFDM) scheme to frequency and time variations but at the same time introduce correlation between subcarriers that destroys the orthogonality of the system. This correlation is however well defined and can be effectively used at the receiver in the detection process. This paper investigates the performance of OFDM systems when using time-limited waveforms over multipath radio channels. For pulse shaping of the same duration as the OFDM block interval, the memory between the subcarriers can be fully utilized by means of a maximum likelihood sequence estimation (MLSE) detector. It is shown that with such a detector, pulse shaping improve the performance of OFDM systems in multipath radio channels. The obtained results also show the advantage of employing pulse shaping with OFDM systems in the presence of long echoes.
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| 39. |
- Ben Slimane, Slimane, et al.
(författare)
-
Performance of quadrature pulse-overlapping modulated signals in Rayleigh fading channels
- 1991
-
Ingår i: IEEE Global Telecommunications Conference and Exhibition. ; , s. 1802-1806
-
Konferensbidrag (refereegranskat)abstract
- The authors discuss the average bit error probability of constant envelope quadrature pulse-overlapping modulation and maximum likelihood Viterbi decoding in a Rayleigh fading channel. The quadrature pulse-overlapping modulation is first decomposed into a linear encoder followed by a memoryless modulator. An upper bound on the average bit error probability as a function of the transfer function of the linear encoder is then developed under the assumption of using the Viterbi decoder with perfect fading amplitude measurement. Tightness of the bound was examined by means of computer simulation. A performance comparison with conventional quadrature phase shift keying is also provided
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| 40. |
- Ben Slimane, Slimane, et al.
(författare)
-
Performance of Wireless LANs in Radio Channels
- 2000
-
Konferensbidrag (refereegranskat)abstract
- Wireless Local Area Networks (WLANs) are faced with the presence of hid den terminals and the possibility of capture when operating in multipath radio channels. These phenomena complicate both their design and performance anal ysis. This paper considers the performance of wireless LANs with Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol in fading chan nels. To assess the presence of hidden terminals and the possibility of capture, a stochastic channel model between the different stations and between the AP and the stations is used. The system throughput and the average packet delay are evaluated under fading conditions. The obtained results show that fading chan nels affect the system performance and especially for mobile terminals far away from the access point thus creating unfariness within the system.
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| 41. |
- Ben Slimane, Slimane, et al.
(författare)
-
Power optimization of M-PSK cochannel signals for a narrowband multiuser detector
- 2001
-
Ingår i: IEEE Pacific RIM Conference on Communications, Computers, and Signal Processing - Proceedings. ; , s. 247-250
-
Konferensbidrag (refereegranskat)abstract
- An analytical method is presented to determine the optimum received power values for multiple cochannel multilevel phase-shift-keying (M-PSK) modulated signals. The aim is to achieve equal symbol error probability (SEP) for each of the signals when applying a narrowband multiuser detector based on successive cancellations. Power relations based on two approximations are derived and used to compute the average SEP for the different cochannel signals. The derived power relations are also compared against optimum power relations obtained through computer simulations
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| 42. |
|
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| 43. |
- Ben Slimane, Slimane
(författare)
-
Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding
- 2007
-
Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 56:2, s. 686-695
-
Tidskriftsartikel (refereegranskat)abstract
- Orthogonal-frequency-division-multiplexing (OFDM) techniques allow the transmission of high data rates over broadband radio channels subject to multipath fading without the need for powerful channel equalization. However, they are very sensitive to nonlinear effects due to the high peak-to-average power ratio (PAPR) owned by their transmitted signals. This paper proposes an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and, thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this precoding scheme is an attractive solution to the PAPR problem of OFDM signals. It is shown, through computer simulations, that the PAPR of precoded OFDM signals approaches that of single-carrier signals. The good improvement in PAPR given by the present technique permits the reduction of the complexity and cost of the transmitter significantly. The precoding schemes also take advantage of the frequency variations of the communication channel and can provide considerable performance gain in fading-multipath channels.
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| 44. |
- Ben Slimane, Slimane, et al.
(författare)
-
Relay Communication with Delay Diversity for Future Communication Systems
- 2006
-
Ingår i: 2006 IEEE 64TH VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-6. - New York : IEEE. - 1424400627 ; , s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- In this paper we consider relay communication as a way of increasing the diversity gain in fading wireless environments. The idea is to combine relay communication with delay diversity where each relay introduces a certain time delay to the signal before forwarding. The result is an increased frequency selectivity in the relay channel which can be exploited at the receiver. The obtained results show that, for single carrier signals with frequency domain equalization, considerable performance gain is obtained.
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| 45. |
- Ben Slimane, Slimane, et al.
(författare)
-
Tight bounds on the error probability of coded modulation schemes in Rayleigh fading channels
- 1994
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a tight upper bound on the bit error performance of coded modulation schemes in Rayleigh fading channels. Upper and lower bounds on the pairwise error probability are first derived. The upper bound is then expressed in a product form to be used with the transfer function bounding technique. This upper bound has the same simplicity as the union-Chernoff bound while providing closer results to the exact expression. Examples for 4-state and 8-state TCM 8PSK schemes are also given to illustrate the tightness and the application of this upper bound
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| 46. |
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| 47. |
- Bengtsson, Mats, 1967-, et al.
(författare)
-
Recent Advances on MIMO Processing in the SATURN Project
- 2002
-
Ingår i: Proc. IST Mobile Communications Summit.
-
Konferensbidrag (refereegranskat)abstract
- We highlight some recent results on the theory and algorithmsfor MIMO systems, obtained at the Royal Instituteof Technology (KTH) within the SATURN project.The paper includes a a new approximate expression forthe ergodic channel capacity of a MIMO system with correlatedfading, algorithms for MIMO beamforming underEIRP (equivalent isotropic radiated power) constraintsand a low-complexity algorithm for MIMO channel estimationin OFDM systems. Also, we show how transmitand beamformers can be determined in a decentralizedfashion without explicitly estimating the channel response.
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| 48. |
- Berggren, Fredrik, et al.
(författare)
-
A simple bound on the outage probability with lognormal interferers
- 2004
-
Ingår i: IEEE Communications Letters. - : IEEE. - 1089-7798 .- 1558-2558. ; 8:5, s. 271-273
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of determining the outage probability in a cellular radio system, where the interference is modeled by a sum of lognormal random variables. As no closed form expression is known, bounds can serve as a quick way of evaluating performance. By applying the arithmeticgeometric mean inequality, we give a lower bound, computationally simple as it is expressed by a single Q-function. The bound includes the case of correlated interferers and background noise. Numerical evaluation for a range of parameters valid for practical applications, shows good accuracy for moderate variances and improvement over a previously suggested bound. This is especially emphasized when the number of interferers is large.<
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| 49. |
- Berggren, Fredrik, et al.
(författare)
-
Linear Successive Interference Cancellation in DS-CDMA Systems
- 2003
-
Ingår i: Wireless Communications & Mobile Computing. - : Wiley. - 1530-8669 .- 1530-8677. ; 3:7, s. 847-859
-
Tidskriftsartikel (refereegranskat)abstract
- Successive interference cancellation techniques have the potential to reduce the interference and therefore increase the capacity of cellular radio systems. In this work, we analyze a linear DS-CDMA receiver utilizing soft feedback interference cancellation. To be able to meet diverse QoS requirements, we introduce a power control scheme that takes into account heterogeneous service levels as well as the impact of imperfect interference cancellation. We address the capacity resulting from this receiver and give its user capacity region on closed-form. We show that our results are general and provide a framework for capacity comparison for many proposed linear successive cancellation receiver models. Several receiver modifications are included, partial interference cancellation; when only part of the signal is canceled, and limited cancellation; when not every signal is canceled. We derive the minimum power solution of a single-cell, from which convergent multicellular distributed power control algorithms that iteratively update the powers are suggested. The numerical results show that there are large gains in user capacity from interference cancellation when the Eb/Io requirements are high. However, regardless of the required targets the maximum capacity is always achieved through partial successive interference cancellation. It is also found that the power levels are sensitive to the cancellation effciency and worse performance than single-user detection can occur.
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| 50. |
- Berggren, Fredrik, et al.
(författare)
-
Power Allocation for a Simple Successive Interference Cancellation Scheme in a Multi-Rate DS-CDMA System
- 2002
-
Ingår i: 2002 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-5, CONFERENCE PROCEEDINGS. - New York : IEEE. - 0780374002 ; , s. 351-355
-
Konferensbidrag (refereegranskat)abstract
- We investigate a multi-rate receiver utilizing soft feedback successive interference cancellation. To be able to meet the QoS requirements for each user, the multiuser detection is done in conjunction with power control. For this, we introduce a power control scheme that takes into account the respective QoS requirements and the impact of imperfect interference cancellation. We derive the minimum power solution, from which distributed iterative power control algorithms are suggested. It is found that the rate of convergence of the power control can be accelerated if the cancellation efficiency parameter can be directly incorporated into the power update. We also address the capacity resulting from this receiver in terms of the notion of effective bandwidth [1].
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