A self-organizing load balancing framework is proposed in this paper. It provides self-optimizing load balancing policies to improve adaptation and robustness of Fixed Relay Station (FRS) based cellular networks. The framework proposes a Self-organizing Cooperative Partner Cluster (SCPC) concept to dynamically select optimal partners of each BS and RS. A novel Comprehensive Load Balancing Policy Stack (CLBPS) is also proposed to utilize merits of various load balancing policies. Load balancing performance, signaling costs and user experience are taken into account in both SCPC and CLBPS. Simulation results show that the call blocking rate is reduced and the network throughput of FRS networks is improved.

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Self-organizing Load Balancing for Relay Based Cellular Networks

We address the problem of frequency reuse schemes in the downlink of the fixed two-hop orthogonal frequency division multiple access (OFDMA) cellular relaying networks. There has been little work on specific frequency reuse schemes for this system in the literatures, although this is the key element for realizing the potential capacity and coverage increase offered by the relay. Therefore, we propose a novel frequency reuse scheme for spectrum efficiency enhancement. Based on this scheme, inter-cell interference (ICI) and SINR received by one- hop and two-hop users are analyzed. System-level simulation results show that our presented frequency reuse scheme can achieve significant improvement on spectrum efficiency compared to modified soft frequency reuse (MSFR) scheme.

A Novel Frequency Reuse Scheme for OFDMA Based Relay Enhanced Cellular Networks

Mobility load balancing (MLB) is an effective method employed by 3GPP to transfer traffic from a hot-spot cell to neighbouring cells. This paper designs a cooperative mobility load balancing (CMLB) scheme in relay cellular networks. After partner cell selection, in the traffic shifting stage, the partner cell analyses hot-spot cell's traffic shifting request and the idle spectrum of relay station (RS), in order to address the RS aggravating load problem and improve the handover performance. Simulation results show that the proposed CMLB scheme can mitigate the RS aggravating load problem and also reduce the handover failure rate.

Cooperative mobility load balancing in relay cellular networks

Hybrid wireless networks combining the advantages of both mobile ad-hoc networks and infrastructure wireless networks have been receiving increased attention due to their ultra-high performance. An efficient data routing protocol is important in such networks for high network capacity and scalability. However, most routing protocols for these networks simply combine the ad-hoc transmission mode with the cellular transmission mode, which inherits the drawbacks of ad-hoc transmission. This paper presents a Distributed Three-hop Routing protocol (DTR) for hybrid wireless networks. To take full advantage of the widespread base stations, DTR divides a message data stream into segments and transmits the segments in a distributed manner. It makes full spatial reuse of a system via its high speed ad-hoc interface and alleviates mobile gateway congestion via its cellular interface. Furthermore, sending segments to a number of base stations simultaneously increases throughput and makes full use of widespread base stations. In addition, DTR significantly reduces overhead due to short path lengths and the elimination of route discovery and maintenance. DTR also has a congestion control algorithm to avoid overloading base stations. Theoretical analysis and simulation results show the superiority of DTR in comparison with other routing protocols in terms of throughput capacity, scalability, and mobility resilience. The results also show the effectiveness of the congestion control algorithm in balancing the load between base stations.

A Distributed Three-Hop Routing Protocol to Increase the Capacity of Hybrid Wireless Networks

In a multi-cell scenario, the inter-cell interference (ICI) is detrimental in achieving the intended system performance, in particular for the edge users. There is paucity of work available in literature on ICI coordination (ICIC) for relay-assisted cellular networks (RACN). In this paper, we do a survey on the ICIC schemes in cellular networks and RACN. We then propose a self-organized resource allocation plan for RACN to improve the edge user's performance by ICIC. We compare the performance of reuse-1, reuse-3, soft frequency reuse (SFR) scheme, proposed plan with and without relays. The performance metrics for comparison are edge user's spectral efficiency, their signal-to-interference-and-noise ratio (SINR) and system's area spectral efficiency. We show by the simulation results that our proposed plan performs better than the existing resource allocation schemes in static allocation scenario. Next, we propose to make our resource allocation plan dynamic and self-organized. The distinct features of our proposed plan are: One, it achieves a trade-off between the system's area spectral efficiency and the edge user's spectral efficiency performance. Secondly, it introduces a novel concept of interfering neighbor set to achieve ICIC by local interaction between the entities.

A Self-Organized Resource Allocation using Inter-Cell Interference Coordination (ICIC) in Relay-Assisted Cellular Networks

Radio frequency allocation is of great importance in the multihop cellular network, because some extra resources (frequency or time slot) seem to be allocated to the relay station. Generally, the tradeoff must be made between the frequency reuse factor and the inter-cell interferences during establishing frequency allocation scheme. A "pre-configured and fixed (PreF)" frequency allocation scheme has been proposed in [1]. In this paper, the concept of "soft frequency reuse (SFR)" in [2] is first borrowed, and applied to the multihop cellular network. After that, the improvement is made to the SFR scheme, and a more efficient "modified SFR (MSFR)" frequency allocation scheme is proposed. Through the simulations, it is demonstrated that, almost the same cell throughput can be achieved in the PreF and SFR schemes for the uniform traffic distribution, and the MSFR scheme can provide nearly twice cell throughput as large as that in the aforementioned two schemes. Moreover, the SFR and MSFR schemes both outperform the PreF scheme for the non-uniform traffic distribution because of the support to dynamic frequency resource allocation in the proposed schemes.

Spectral Efficient Frequency Allocation Scheme in Multihop Cellular Network

In this paper, the sum rate issue of a multiple-input multiple-output (MIMO) relay broadcast channel is studied, where the fixed relay station is used to support multiuser transmission in a downlink channel With appropriate design, the sum rate can be expressed as a function of the processing units at the base station (BS) and relay, and the power allocation can be converted to a standard convex problem We compared the sum rate of MIMO relay broadcast channel (BC) using time division multiple access (TDMA) to the strongest user, dirty paper coding (DPC) and beamforming (BF) when multiple antennas are deployed at each terminal in the system and separate power constraints at the BS and relay Then, the sum rate bounds for each strategy and the sum capacity (achieved by DPC) gain over TDMA and BF are given, correspondingly Finally, numerical results are presented to prove our discussions With these results, we can easily obtain how far away TDMA and BF are from being optimal in terms of sum rate, and direct the practical system design

Lei Guan

Papers

Spectral Efficient Frequency Allocation Scheme in Multihop Cellular Network

A Comparison of Broadcast Strategy in MIMO Relay Networks