TL;DR: This paper studies the downlink capacity of edge users in a cellular network and sees whether base station cooperation improves the spectral efficiency, and proposes Selective Cooperation, where the selection criteria is based on throughput.
Abstract: Cooperative transmission schemes are used in wireless networks to improve the spectral efficiency. In a multi-cell environment, inter-cell interference degrades the performance of wireless systems. In this paper, we study the downlink capacity of edge users in a cellular network and see whether base station cooperation improves the spectral efficiency. The base-stations coordinate their transmission to the two cell-edge users in order to improve their Signal-to-interference-noise ratio (SINR) and throughput. Selective Cooperation, where the selection criteria is based on throughput, is proposed. The capacity achieved through Cooperation is shared equally among the cell-edge users. Results show that, the proposed hybrid scheme, provides a better result compared to full-time cooperation. Finally, an example from UMTS is presented.
TL;DR: Although the outage performance of the proposed approach is poorer than the joint transmission mode of a cooperative multipoint scheme in lightly loaded networks, its effective capacity is significantly higher under varying network traffic load and QoS constraints.
Abstract: In this paper, we present a quality-of-service (QoS)-aware cooperative downlink scheduling approach for cell-edge and handoff users that offers more reliability and higher effective capacity. The cooperation (handoff) region is defined for active handoff users between two adjacent base stations (BSs) as a function of the user QoS requirements and network load. In addition, the proposed technique inherently acquires intercell interference (ICI) coordination by adjusting the position and size of the cooperation window suitably. Numerical results are presented showing reliability, user QoS and capacity gain performance, and the region for cooperative scheduling in a coded communication scenario. Our analysis indicates that cooperation provides relatively less gain in effective capacity, i.e., up to about 40% with respect to noncooperative handoff, when the QoS requirement is loose. On the other hand, when the QoS requirement is more stringent, the effective capacity gain can increase up to nearly 100%. Additionally, we show that, while for applications with a loose QoS requirement the cooperation window size is small, i.e., nearly 1% of the total area of the BSs participating in cooperation, it increases quite significantly, i.e., up to nearly 25%, for the applications with stringent QoS. Although the outage performance of the proposed approach is poorer than the joint transmission mode of a cooperative multipoint scheme in lightly loaded networks, its effective capacity is significantly higher under varying network traffic load and QoS constraints.
TL;DR: In this paper, the authors proposed a method, system and transmitter for adaptive coordinated transmission in wireless communications, which includes configuring one of the more than one transmitter to be a serving transmitter with others of the other transmitter being cooperating transmitters.
Abstract: Embodiments of the present invention include a method, system and transmitter for adaptive coordinated transmission in wireless communications. The method includes: determining more than one transmitter for performing coordinated transmission, configuring one of the more than one transmitter to be a serving transmitter with others of the more than one transmitter being cooperating transmitters, and determining more than one receiver; determining, by a cooperating transmitter, a cooperation mode according to measured signal parameters of the more than one receiver after receiving a cooperation request from the serving transmitter, and providing the cooperation mode to the serving transmitter; generating, by each of the more than one transmitter, a transmit signal corresponding to the more than one receiver according to the cooperation mode determined, and transmitting the transmit signal to each of the more than one receiver. The method, system and transmitter of the present invention increase spectrum efficiency for cell edge users as much as possible while having relatively low implementation complexity.
TL;DR: A differentiated QoS provisioning approach that accounts for the MS speed, its channel quality, as well as the loads at different BSs is provided, and the benefits of the proposed class-based split handoff approach is demonstrated.
Abstract: In this paper, we present a new resource allocation scheme for cell-edge active users to achieve improved performance in terms of a higher system capacity and better quality-of-service (QoS) guarantee of the users, where we utilize the two-dimensional resource allocation flexibility of orthogonal frequency division multiple access (OFDMA) networks. Here, the mobile stations (MSs) at the cell-edge can maintain parallel connections with more than one base station (BS) when it is in their coverage area. A MS, before handoff to a new BS, seeks to utilize additional resources from the other BSs if the BS through which its current session is registered is not able to satisfy its requirements. The handoff procedure is termed as split handoff. The BSs participate in split handoff operation while guaranteeing that they are able to maintain QoS of the existing connections associated with them. In this study, first, we present the proposed shared resource allocation architecture and protocol functionalities in split handoff, and give a theoretical proof of concept of system capacity gain associated with the shared resource allocation approach. Then, we provide a differentiated QoS provisioning approach that accounts for the MS speed, its channel quality, as well as the loads at different BSs. Via extensive simulations in Qualnet, the benefits of the proposed class-based split handoff approach is demonstrated. The results also indicate traffic load balancing property of the proposed scheme in heavy traffic conditions.
11 citations
Cites background from "Throughput improvement for cell-edg..."
...Many scheduling techniques have been proposed in the literature which take care of user-level fairness and network capacity [4], [5],
....
TL;DR: A GCCA-based method is put forth that leverages selective BS cooperation to recover the cell-edge user signal subspace even at low SNR, and it is shown that using the closest three BS is always the best choice.
Abstract: Improving the uplink quality of service for users located around the boundaries between cells is a key challenge in cellular systems. Existing approaches relying on power control throttle the rates of cell-center users, while multi-user detection requires accurate channel estimates for the cell-edge users, which is another challenge due to their low received signal-to-noise ratio (SNR). Utilizing the fact that cell-edge user signals are weak but common (received at roughly equal power) at different base stations (BSs), this paper establishes a connection between cell-edge user detection and generalized canonical correlation analysis (GCCA). It puts forth a GCCA-based method that leverages selective BS cooperation to recover the cell-edge user signal subspace even at low SNR. The cell-edge user signals can then be extracted from the resulting mixture via algebraic signal processing techniques. The paper includes theoretical analysis showing why GCCA recovers the correct subspace containing the cell-edge user signals under mild conditions. The proposed method can also identify the number of cell-edge users in the system, i.e., the common subspace dimension. Simulations reveal significant performance improvement relative to various multiuser detection techniques. Cell-edge detection performance is further studied as a function of how many / which BSs are selected, and it is shown that using the closest three BS is always the best choice.
6 citations
Cites background from "Throughput improvement for cell-edg..."
...gov) variety of techniques, ranging from multi-user detection [9], user scheduling [10], power control [11], cooperative communication [6], [12], and interference mitigation [13]–[15] have been proposed as possible candidates for tackling this problem....
TL;DR: An efficient proportional fair scheduling algorithm for Orthogonal Frequency Division Multiple Access (OFDMA) based cooperative cellular networks is proposed and shows that the proposed scheme significantly increases the cell-edge throughput and guarantees system fairness.
Abstract: Multi-cell cooperative transmission schemes are considered as promising candidates in future 4G wireless networks (LTE-Advanced) to combat the inter-cell interference that degrades the cell-edge throughput performance. An efficient proportional fair (PF) scheduling algorithm for Orthogonal Frequency Division Multiple Access (OFDMA) based cooperative cellular networks is proposed. A PF metric maximization problem is first formulated. Then a two-step algorithm is proposed to solve the problem: the user grouping step and the user scheduling step. The simulation results show that the proposed scheme significantly increases the cell-edge throughput and guarantees system fairness.
5 citations
Cites background from "Throughput improvement for cell-edg..."
...Also in a full-frequency reuse network, the other cell interference degrades the system performance and especially the cell-edge throughput....
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...Simulation results are given in Section IV and some concluding remarks are provided in Section V....
TL;DR: Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.
Abstract: Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. In this two-part paper, we propose a new form of spatial diversity, in which diversity gains are achieved via the cooperation of mobile users. Part I describes the user cooperation strategy, while Part II (see ibid., p.1939-48) focuses on implementation issues and performance analysis. Results show that, even though the interuser channel is noisy, cooperation leads not only to an increase in capacity for both users but also to a more robust system, where users' achievable rates are less susceptible to channel variations.
6,621 citations
"Throughput improvement for cell-edg..." refers background in this paper
...Cooperative transmission utilizes the inherent user diversity available in a multi-user environment to provide higher spectral efficiency [1–3]....
TL;DR: An overview of the developments in cooperative communication, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenn transmitter that allows them to achieve transmit diversity.
Abstract: Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenna transmitter that allows them to achieve transmit diversity. This article presents an overview of the developments in this burgeoning field.
3,130 citations
"Throughput improvement for cell-edg..." refers background in this paper
...Cooperative transmission utilizes the inherent user diversity available in a multi-user environment to provide higher spectral efficiency [1–3]....
TL;DR: Two variants of an energy-efficient cooperative diversity protocol are developed that combats fading induced by multipath propagation in wireless networks and can lead to reduced battery drain, longer network lifetime, and improved network performance in terms of, e.g., capacity.
Abstract: We develop two variants of an energy-efficient cooperative diversity protocol that combats fading induced by multipath propagation in wireless networks, The underlying techniques build upon the classical relay channel and related work and exploit space diversity available at distributed antennas through coordinated transmission and processing by cooperating radios. While applicable to any wireless setting, these protocols are particularly attractive in ad-hoc or peer-to-peer wireless networks, in which radios are typically constrained to employ a single antenna. Substantial energy-savings resulting from these protocols can lead to reduced battery drain, longer network lifetime, and improved network performance in terms of, e.g., capacity.
688 citations
"Throughput improvement for cell-edg..." refers background in this paper
...Cooperative transmission utilizes the inherent user diversity available in a multi-user environment to provide higher spectral efficiency [1–3]....
TL;DR: Holma et al. as mentioned in this paper proposed a radio resource management architecture for HSDPA and showed that HSUPA bit rates, capacity and coverage can be improved by using IP header compression.
Abstract: Preface. Acknowledgements. Abbreviations. 1. Introduction (Harri Holma and Antti Toskala). 1.1 WCDMA technology and deployment status. 1.2 HSPA standardization and deployment schedule. 1.3 Radio capability evolution with HSPA. 2. HSPA standardization and background (Antti Toskala and Karri Ranta-Aho) 2.1 3GPP. 2.2 References. 3. HSPA architecture and protocols (Antti Toskala and Juho Pirskanen). 3.1 Radio resource management architecture. 3.2 References. 4. HSDPA principles (Juho Pirskanen and Antti Toskala). 4.1 HSDPA vs Release 99 DCH. 4.2 Key technologies with HSDPA. 4.3 High-speed dedicated physical control channel. 4.4 BTS measurements for HSDPA operation. 4.5 Terminal capabilities. 4.6 HSDPA MAC layer operation. 4.7 References. 5. HSUPA principles (Karri Ranta-Aho and Antti Toskala). 5.1 HSUPA vs Release 99 DCH. 5.2 Key technologies with HSUPA. 5.3 E-DCH transport channel and physical channels. 5.4 Physical layer procedures. 5.5 MAC layer. 5.6 Iub parameters. 5.7 Mobility. 5.8 UE capabilities and data rates. 5.9 References and list of related 3GPP specifications. 6. Radio resource management (Harri Holma, Troels Kolding, Klaus Pedersen, and Jeroen Wigard). 6.1 HSDPA radio resource management. 6.2 HSUPA radio resource management. 6.3 References. 7. HSDPA bit rates, capacity and coverage (Frank Frederiksen, Harri Holma, Troels Kolding, and Klaus Pedersen). 7.1 General performance factors. 7.2 Single-user performance. 7.3 Multiuser system performance. 7.4 Iub transmission efficiency. 7.5 Capacity and cost of data delivery. 7.6 Round trip time. 7.7 HSDPA measurements. 7.8 HSDPA performance evolution. 7.9 Conclusions. 7.10 Bibliography. 8. HSUPA bit rates, capacity and coverage (Jussi Jaatinen, Harri Holma, Claudio Rosa, and Jeroen Wigard). 8.1 General performance factors. 8.2 Single-user performance. 8.3 Cell capacity. 8.4 HSUPA performance enhancements. 8.5 Conclusions. 8.6 Bibliography. 9. Application and end-to-end performance (Chris Johnson, Sandro Grech, Harri Holma, and Martin Kristensson) 9.1 Packet application introduction. 9.2 Always-on connectivity. 9.3 Application performance over HSPA. 9.4 Application performance vs network load. 9.5 References. 10. Voice-over-IP (Harri Holma, Esa Malkama ki, and Klaus Pedersen). 10.1 VoIP motivation. 10.2 IP header compression. 10.3 VoIP over HSPA. 10.4 References. 11. RF requirements of an HSPA terminal (Harri Holma, Jussi Numminen, Markus Pettersson, and Antti Toskala). 11.1 Transmitter requirements. 11.2 Receiver requirements. 11.3 Frequency bands and multiband terminals. 11.4 References. Index.
TL;DR: It is argued that many of the traditional interference management techniques have limited usefulness when viewed in concert with MIMO, and emerging system-level interference-reducing strategies based on cooperation will be important for overcoming interference in future spatial multiplexing cellular systems.
Abstract: Multi-antenna transmission and reception (known as MIMO) is widely touted as the key technology for enabling wireless broadband services, whose widespread success will require 10 times higher spectral efficiency than current cellular systems, at 10 times lower cost per bit. Spectrally efficient, inexpensive cellular systems are by definition densely populated and interference-limited. But spatial multiplexing MIMO systems- whose principal merit is a supposed dramatic increase in spectral efficiency- lose much of their effectiveness in high levels of interference. This article overviews several approaches to handling interference in multicell MIMO systems. The discussion is applicable to any multi-antenna cellular network, including 802.16e/WiMAX, 3GPP (HSDPA and 3GPP LTE), and 3GPP2 (lxEVDO). We argue that many of the traditional interference management techniques have limited usefulness (or are even counterproductive) when viewed in concert with MIMO. The problem of interference in MIMO systems is too large in scope to be handled with a single technique: in practice a combination of complementary countermeasures will be needed. We overview emerging system-level interference-reducing strategies based on cooperation, which will be important for overcoming interference in future spatial multiplexing cellular systems.
383 citations
"Throughput improvement for cell-edg..." refers methods in this paper
...Cooperative encoding and scheduling in a Networked MIMO system is discussed in [6], in order to supress Other Cell Interference (OCI) and thereby achieve maximum capacity in MIMO downlink channel....