| 1. |
- Uhlemann, Elisabeth, et al.
(author)
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Deadline dependent coding-a framework for wireless real-time communication
- 2000
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In: Seventh International Conference on Real-Time Computing Systems and Applications. - Piscataway, NJ : IEEE. - 0769509304 ; , s. 135-142, s. 135-142
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Conference paper (peer-reviewed)abstract
- A framework for real-time communication over a wireless channel is proposed. The concept of deadline dependent coding (DDC), previously suggested by the authors, is further developed using soft decision decoding of block codes to maximize the probability of delivering information before a given deadline. The strategy of DDC is to combine different coding and decoding methods with automatic repeat request (ARQ) in order to fulfil the application requirements. These requirements are formulated as two Quality of Service (QoS) parameters: deadline (t_DL) and probability of correct delivery before the deadline (P_d), leading to a probabilistic view of real-time communication. An application can negotiate these QoS parameters with the DDC protocol, thus creating a flexible and dependable scheme.
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| 2. |
- Alexander, Paul D., et al.
(author)
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Filter structure for iterative signal processing
- 2002
-
Patent (pop. science, debate, etc.)abstract
- The present invention relates to improved multiple access communications. In one form, the invention relates to an improved signal processing method and apparatus for an iterative method of determining the reception of a signal in a multi user packet based wireless OFDM (Orthogonal Frequency Division Multiplexing) communication system. In other forms the present invention provides recursive filtering for joint iterative decoding in a variety of systems and functions such as linear multiple access channel decoders, iterative equalisation, iterative joint channel estimation and detection/decoding, iterative space-time processing, iterative multi user interference cancellation and iterative demodulation.; In one particular form the present invention provides an iterative decoding circuit for a wireless multiuser communications receiver comprising a first signal processing means for receiving at least one received signal, said first signal processing means comprising at least two linear iterative filters such that the first linear iterative filter provides an estimate of a selected received signal to an estimated signal output and a second linear iterative filter provides estimates of at least one other received signal, delayed by one iteration cycle, to an input of said first linear iterative filter, a second signal processing means for receiving the estimated signal output of the first linear iterative filter and providing a further received signal estimate to the input of the first signal processing means in a succeeding iteration cycle of the decoding circuit.
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| 3. |
- Alexander, Paul D., et al.
(author)
-
Filter structure for iterative signal processing
- 2002
-
Patent (pop. science, debate, etc.)abstract
- The invention is an iterative signal processing arrangement having one or more pairs of first and second signal processing components. These pairs are in iterative configuration with each of the first signal processing components having as its input one or more received signals dependent upon one or more transmitted signals. For each said signal processing component pair the output of said first signal processing component is an estimate of a characteristic of a selected transmitted signal based on the current and one or more previous input signals received by said first signal processing component. This estimate is input to said corresponding second signal processing component which provides a further estimate of said selected transmitted signal. The outputs of all said second components of respective pairs are input to their corresponding first components in a succeeding iteration cycle.
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| 4. |
- Brännström, Fredrik, 1974, et al.
(author)
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Capacity considerations for trellis code multiple access systems
- 2001
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In: IEEE Information Theory Workshop (ITW ’01), Cairns, Australia, Sept. 2001. ; , s. 153–-155, s. 153-155
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Conference paper (peer-reviewed)abstract
- Trellis code multiple access (TCMA) is anarrow-band multiple access scheme. There is no bandwidthexpansion, so K users are using the same bandwidthas one single user. The load (the number of bits per channeluse) of the system is therefore much higher than the loadin, for example, conventional CDMA systems. It is shownhere that the maximum number of users in a TCMA systemis usually modest. This fact is based on constellationconstrainedcapacity, i.e., the maximum capacity of a systemwith a specific constellation of the transmitted symbols.The minimum required signal-to-noise ratio for reliabletransmission is also given for different code rates.
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| 5. |
- Brännström, Fredrik, 1974, et al.
(author)
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Constellation-constrained capacity for trellis code multiple access systems
- 2001
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In: IEEE Global Telecommunications Conference (GLOBECOM ’'01), San Antonio, TX, Nov. 2001. ; , s. 791-–795, s. 791-795
-
Conference paper (peer-reviewed)abstract
- Trellis code multiple access (TCMA) is a narrow-band multipleaccess scheme. There is no bandwidth expansion, soK users are usingthe same bandwidth as one single user. The load (the number of bits perchannel use) of the system is therefore much higher than the load in, forexample, conventional CDMA systems. It is shown here that the maximumnumber of users in a TCMA system is usually modest. This fact is basedon constellation-constrained capacity, i.e., the maximum capacity of a systemwith a specific constellation of the transmitted symbols. The minimumrequired signal-to-noise ratio for reliable transmission is also given for differentcode rates.
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| 6. |
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| 7. |
- Brännström, Fredrik, 1974, et al.
(author)
-
Convergence analysis of iterative detectors for narrow-band multiple access
- 2002
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In: IEEE Global Telecommunications Conference (GLOBECOM '02), Taipei, Taiwan, Nov. 2002. ; , s. 1373-–1377
-
Conference paper (peer-reviewed)abstract
- Convergence analysis of iterative detectorsfor narrow-band multiple access is performed by usingextrinsic information transfer charts. The system has nobandwidth expansion, so K users are using the same bandwidthas one single user. The load (the number of bitsper channel use) of the system is therefore higher than theload in, for example, conventional CDMA systems. Theanalysis provide useful guidelines how to combine outercodes with the chosen mapper for different loads of thesystem. Both memoryless mappers and differential mappersare evaluated. The limitations of the system measuredin the maximum number of users and the requiredSNR for different scenarios are presented.
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| 8. |
- Brännström, Fredrik, 1974, et al.
(author)
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Extrinsic information transfer charts for narrow-band multiple access
- 2002
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In: Radio Science and Communication (RVK'02), Stockholm, Sweden, June 2002. ; , s. 719–-723
-
Conference paper (peer-reviewed)abstract
- Convergence analysis of iterative detectors for narrowband multiple access is performed by using extrinsicinformation transfer charts. The system has no bandwidth expansion, so K users are using the same bandwidth as one single user. The load (the number of bitsper channel use) of the system is therefore higher thanthe load in, for example, conventional CDMA systems.The analysis provide useful guidelines how to combineouter codes with the chosen mapper for different loadsof the system. Both memoryless mappers and differential mappers are evaluated. The limitations of thesystem measured in the maximum number of users andthe required SNR for different scenarios are presented.
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| 9. |
- Brännström, Fredrik, 1974, et al.
(author)
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Iterative detectors for trellis-code multiple-access
- 2002
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In: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 50:9, s. 1478–-1485
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Journal article (peer-reviewed)abstract
- Trellis-code multiple-access (TCMA) is a narrowbandmultiple-access scheme based on trellis-coded modulation.There is no bandwidth expansion, so K users occupy the samebandwidth as one single user. The load of the system, in number of bits per channel use, is therefore much higher than the load in, for example, conventional code-division multiple-access systems. Interleavers are introduced as a new feature to separate the users. This implies that the maximum-likelihood sequence detector (MLSD) is now too complex to implement. Iterative detectors are therefore suggested as an alternative to the joint MLSD. Theconventional interference cancellation (IC) detector has lower complexity than the MLSD, but its performance is shown to be far from acceptable. Even after a novel improvement of the IC detector, the performance is unsatisfactory. Instead of using IC, another iterative detector is suggested. This detector updates the branch metric for every iteration, and avoids the standard Gaussian approximation. Simulations show that the performance of this detector can be close to single-user performance, even when the interleaver and the phase offset are the only user-specific features in the TCMA system.
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| 10. |
- Brännström, Fredrik, 1974, et al.
(author)
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Iterative multi-user detection of trellis code multiple access using a posteriori probabilities
- 2001
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In: IEEE International Conference on Communications (ICC ’'01), Helsinki, Finland, June 2001. ; , s. 11–-15, s. 11-15
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Conference paper (peer-reviewed)abstract
- Iterative detectors for trellis code multiple access (TCMA) aresuggested as an alternative to the joint maximum likelihood sequence detector(MLSD). Interleavers are introduced in the TCMA system as a newfeature to separate the users. This implies that MLSD is now too complexto implement. The conventional interference cancellation (IC) detector haslower complexity, but its performance is shown to be far from acceptable.Another iterative detector having close to single user performance is thereforesuggested. Instead of using IC, this detector updates the branch metricfor every iteration and avoids the standard Gaussian approximation. It isalso shown that the users can be detected when the interleaver is the onlyuser specific feature in the TCMA system.
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