| 1. |
- Burr, Alister, et al.
(författare)
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MIMO Truncated Shannon Bound for System Level Capacity Evaluation of Wireless Networks
- 2012
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Ingår i: IEEE Wireless Communications and Networking Conference, Paris, France, Apr. 2012. - 9781467306829 ; , s. 268-272
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Konferensbidrag (refereegranskat)abstract
- We outline a general method for modelling the capacity of a MIMO link within a wireless, assuming that capacity of a link is a random function of SNR and signal to interference ratio (SIR), since the maximum link throughput depends on the random channel of both the user's signal and the interference. We show how a look-up table for the CDF of this random function can be obtained by link-level simulation in the presence of interference having the same characteristics as the interference found in the target network. We also exploit the Truncated Shannon Bound (TSB) to estimate the resulting capacity obtained in practice in a system using adaptive modulation and coding on the link level.
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| 2. |
- Lakshmana, Tilak Rajesh, 1980, et al.
(författare)
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On the Potential of Broadcast CSI for Opportunistic Coordinated Multi-Point Transmission
- 2012
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Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - 9781467325691 ; , s. 1262-1267
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Konferensbidrag (refereegranskat)abstract
- Coordinated Multi-Point transmission is a promising technique to improve the performance of the users at the cell-edge. To achieve this, in case of a centralized approach, users need to unicast the quantized channel state information (CSI), typically to the anchor base station (BS), and then each BS forwards this information to a central coordination node for precoding and scheduling. In the case of a decentralized approach, users broadcast the quantized CSI such that the coordinating BSs could simultaneously receive the CSI. The advantage of a decentralized approach is that it does not require a central coordination node, thereby not imposing stringent latency constraints on the backhaul. The CSI transmission over the erroneous feedback channel in the uplink gives rise to precoding loss and scheduling loss. In the decentralized framework, the feedback errors could result in BSs receiving a different version of the CSI. In this work, we propose a decentralized opportunistic scheduling approach, which only requires a minimal sharing of scheduling information between BSs. The results show that the sum rate achieved with the proposed method is comparable to that of the centralized approach even when there is a high bit error probability introduced by the feedback channel. We also show that when the bit error probabilities in the feedback channel are less than 10^{-4}, the decentralized approach achieves the sum rate of the centralized approach.
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| 3. |
- Li, Jingya, 1986, et al.
(författare)
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Performance evaluation of coordinated multi-point transmission schemes with predicted CSI
- 2012
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Ingår i: IEEE Conference on Personal, Indoor and Mobile Radio Communications, PIMRC, Sydney, Australien. - 9781467325691 ; , s. 1055-1060
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Konferensbidrag (refereegranskat)abstract
- Coordinated multi-point (CoMP) transmission is considered as an efficient technique to improve cell-edge performance as well as system spectrum efficiency. In CoMP-enabled systems, a cluster of coordinated base stations (BSs) are typically assumed to be connected to a control unit (CU) via backhaul links, and the provided performance gain relies heavily on the quality of the channel state information (CSI) available at the CU side. In this paper, we consider the downlink of a CoMP cluster and compare three different CoMP transmission schemes: zero-forcing coherent joint transmission, non-coherent joint transmission and coordinated scheduling. Moreover, for each of the analyzed schemes, the performance in terms of average sum rate of the CoMP cluster is studied with predicted CSI, considering the effects of the feedback and backhaul latency, as well as the user mobility. Compared to zero-forcing coherent joint transmission, we show that non-coherent joint transmission and coordinated scheduling are more robust to channel uncertainty. In addition, depending on the latency, user mobility and user locations, different schemes would achieve the highest average sum rate performance. Hence, a system could switch between the transmission schemes to improve the sum rate.
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| 4. |
- Papadogiannis, Agisilaos, 1982
(författare)
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Advanced Coordinated Multi-Point Techniques for Wireless Networks
- 2012
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- The constantly increasing demand for wireless services, the scarcity of radio spectrum and the characteristics of the global wireless market, necessitate that future wireless systems provide higher peak data rates, better quality-of-service and are more spectrally efficient. A very promising technology that can achieve the aforementioned targets is Coordinated Multi-Point (CoMP). CoMP can mitigate inter-cell interference and augment data rates without sacrificing additional spectrum at the cost of increased overheads and costs. In CoMP systems, base stations (BSs) are grouped into cooperation clusters and the BSs of each cluster exchange information and jointly process signals. Unlike conventional cellular systems, users receive useful signals from several BSs. The aim of this thesis is to facilitate the incorporation of CoMP by practical systems. To this end, a number of advanced CoMP techniques are proposed that strike a very good balance between achievable performance, overheads and costs.
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| 5. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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Advanced Relaying Concepts for Future Wireless Networks
- 2012
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Ingår i: Future Network and Mobile Summit (FUNEMS 2012), Berlin, Germany, July 2012. - 9781905824298
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Konferensbidrag (refereegranskat)abstract
- Relaying is undoubtedly a key technology for future wireless networks as it can be applied to provide coverage extension and capacity increase in a cost-effective manner. This paper presents an outline of the major advanced relaying concepts that will be part of future systems from the viewpoint of the ARTIST4G European project. These concepts can be divided into three categories, those pertinent to type-1 relays, type-2 relays and moving relays. The characteristics of each of these concepts are presented and the challenges related to their implementation are discussed. Furthermore the paper proposes a set of solutions to address the discussed challenges. For type-1 relays, the paper presents solutions for the allocation of resources to the backhaul and the access links, the inter-relay interference mitigation, and the multi-hop transmission mode. For type-2 relays, our focus is on the design of distributed hybrid automatic repeat request (HARQ) protocols. More specifically we propose that the conventional HARQ schemes are adapted to exploit the potentially better channel conditions provided by the relays. Moreover distributed turbo coding solutions are introduced for increasing transmission reliability with the aid of relays. Finally, moving relays are presented as an efficient solution to the ever-growing demand for wireless broadband by users within public transportation vehicles. We show that moving relays can very effectively overcome vehicle penetration losses and boost the achievable capacities of the moving users. Overall, we conclude that the presented advanced relaying concepts are very promising and can significantly enhance the user experience in future wireless networks.
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| 6. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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Bringing Mobile Relays for Wireless Access Networks into Practice - Learning When to Relay
- 2012
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Ingår i: IET Communications. - : Institution of Engineering and Technology (IET). - 1751-8628 .- 1751-8636. ; 6:6, s. 618-627
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Tidskriftsartikel (refereegranskat)abstract
- Adding fixed relay nodes (RNs) to wireless access networks requires additional costly infrastructure. Utilising mobile RNs, that is, user terminals that relay signals intended for other users being the destination nodes (DNs), is an appealing cost-effective solution. However, the changing node topology increases the required signalling for relay selection (RS). The signalling overhead consists of control signals that need to be exchanged between the RNs, the source node (SN) and the DN, to achieve the objectives of cooperation. To reduce signalling without penalising performance, the authors propose a three-step approach exploiting statistical knowledge on the likelihood of attaining performance gains by using RNs as a function of the node position (position of DNs and RNs). In the first step only the cell DNs that are likely to gain from relaying request the assistance of RNs. In the second step, for each DN that requests relaying, a limited set of RN candidates is formed. These decisions are made with the aid of thresholds applied to inter-node distances whose values are based on the acquired statistical knowledge. In the final step, RN candidates feed back the relevant channel state information to the SN that performs RS. Furthermore, the authors investigate the attained gains from mobile RNs as a function of the fading environment and they show that mobile RNs can help overcome the effects of severe fading.
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| 7. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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On the Maximum Achievable Sum-Rate of Interfering Two-Way Relay Channels
- 2012
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 16:1, s. 72-75
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchical networks can provide very high data rates to multiple mobile stations (MSs) through a dense network of fixed relay nodes (RNs) fed by few hub base stations (HBSs). In order to achieve high spectral efficiencies RNs can act as two-way RNs. However the dense RN deployment gives rise to high co-channel interference (CCI) that limits sum-rate performance. In this letter we consider a simple hierarchical network consisting of an HBS with two highly directional antennas communicating with two MSs via two interfering two-way RNs. To mitigate CCI and boost sum-rates we propose a two-way relaying strategy based on AF combined with Network MIMO processing which is applied over the concatenation of the backhaul and access network channels. We compare our proposed strategy with a baseline DF approach and we show that it performs significantly better when CCI is dominant.
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| 8. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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Performance Analysis of Centralized Relay Selection with Unreliable Control Information
- 2012
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781467318808
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Konferensbidrag (refereegranskat)abstract
- The potential of relay selection (RS) has been well appreciated. However if the control channels, conveying information on the selected relay node (RN), are unreliable, the gains of RS diminish. This is because the transmitting RN might not be the one maximizing the employed utility function. Furthermore, more than one of the RNs might end up transmitting, an event that could be performance degrading. It is also likely that no RN transmits, which is very undesirable. In this paper we assume decode-and-forward and present closed form expressions for the outage probability (OP) under Rayleigh fading when two potential RNs are available and the control information related to RS is corrupted by errors. We show that when control channels are unreliable, the OP performance degrades significantly and reaches a floor as the signal-to-noise ratio of the RN-to-destination data channel grows. Furthermore when control channels are very unreliable, suboptimal schemes not requiring control information, like repetition coding, outperform RS.
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| 9. |
- Papadogiannis, Agisilaos, 1982, et al.
(författare)
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The Potential of a Hybrid Fixed/User Relay Architecture -- A Performance Analysis
- 2012
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781467318808
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Konferensbidrag (refereegranskat)abstract
- Future wireless systems are likely to comprise a dense grid of fixed relay nodes (FRNs) and contain a large number of user terminals (UTs) that can act as user relay nodes (URNs) under certain circumstances. In this paper we argue that significant gains can be attained if FRNs and URNs act together under the umbrella of a hybrid architecture. To this end, we derive closed-form expressions for the outage probability (OP) and an ergodic capacity upper bound of a dual-hop system as a function of the number of FRNs and URNs. For this analysis single relay selection under decode-and-forward and Rayleigh fading are assumed. We show that in low signal-to-noise ratio (SNR), FRNs are much more effective in reducing OP than URNs. In high SNR, URNs are almost equally as effective as FRNs in reducing OP. In terms of ergodic capacity, FRNs achieve higher performance than URNs in all SNR regimes. We conclude that from a system design viewpoint, if the aim is to meet certain quality-of-service constraints, FRNs can be reserved to serve low SNR users, while URNs could be employed when channel conditions to destination UTs are more favorable.
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| 10. |
- Pietsch, Christian, et al.
(författare)
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EU FP7 INFSO-ICT-247223 ARTIST4G, D3.5c Moving Relays and Mobility aspects
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable presents analysis and simulation results related to moving relays and mobility optimization for relay enhanced networks. The results reported in this deliverable are ranging from fundamental performance limits expressed in terms outage probability to practical implementations of the moving relay concepts through architecture discussion, coordinated moving relays and network coded moving relays.
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