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.

https://web.iitd.ac.in/~swadesd/pubs/JNL/Handoff-TVT2015.pdf

QoS-Aware Downlink Cooperation for Cell-Edge and Handoff Users

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.

Method, system and transmitter for adaptive coordinated transmission in wireless communications

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.

Class-Based Shared Resource Allocation for Cell-Edge Users in OFDMA Networks

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.

Cell-Edge Detection via Selective Cooperation and Generalized Canonical Correlation

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.

A low complexity resource scheduler for cooperative cellular networks

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.

/pdf/throughput-improvement-for-cell-edge-users-using-selective-4p5m2nrx7k.pdf

M.R. Ramesh Kumar

Papers

Throughput improvement for cell-edge users using selective cooperation in cellular networks