Base Station Cooperation Schemes Research Articles

A Location-Dependent Base Station Cooperation Scheme for Cellular Networks

The link quality in cellular networks strongly depends on the location of the users relative to the serving and interfering base stations (BSs). This paper proposes a location-dependent BS cooperation scheme for general cellular networks, where BSs are modeled using a stationary point process and the Voronoi diagram forms the cell structure. The cooperation scheme is based on the relative average received signal strength from the three strongest BSs. For the channel model where Rayleigh fading and power-law path loss are considered, each cell is partitioned into three regions based on the relative distance to the three nearest BSs: the cell center region, cell edge region, and cell corner region. The area fraction of each region is tuned by the so-called cooperation level $\gamma \in [ {0},{1}]$ . We study the scheme where users in the above regions receive the non-coherent joint transmission from one, two, and three nearest BSs, respectively. As such, the scheme primarily helps users vulnerable to interference. We analyze the signal-to-interference ratio (SIR) in Poisson networks and show that a moderate $\gamma $ jointly improves the average SIR performance and the network fairness.

Robust receivers for base station cooperation systems

In BS (Base Station) cooperation architectures the MTs (Mobile Terminals) in adjacent cells can operate in the same frequency, with the signal's separation and/or MTs detection being performed by a CPU (Central Processing Unit). This results in a substantial improvement in the overall system's capacity and spectral efficiency when compared to conventional cellular systems. To decrease the data load in the backhaul links, the received signals at a given BS must be sampled and quantized before being sent to the CPU, which results in a significant increase of quantization errors. We consider the uplink of BS cooperation schemes employing SC-FDE (Single-Carrier with Frequency-Domain Equalization) modulations and a detection performed through receivers based on the IB-DFE (Iterative Block Decision Feedback Equalization) concept. We present accurate approaches for obtaining the spectral characterization of the quantization noise. Moreover, we propose the design of robust receivers that can take into account the quantization noise effects.1

Comparative study of various multiuser detection and base-station cooperation schemes for uplink multicell systems

In this contribution, we investigate and compare the spectral-efficiency of uplink multicell systems, when various BS cooperation strategies and detection schemes are employed. Associated with our studies, three base-station (BS) operational schemes are considered, which are the ideal BS cooperation, data exchange only and no BS cooperation, in conjunction with four multiuser detection (MUD) schemes, including the optimum MUD (OMUD), OMUD with parallel interference cancellation (OMUD-PIC), linear minimum mean-square error MUD (MMSE-MUD) and the MMSE-based successive interference cancellation (MMSE-SIC). Their spectral-efficiency is evaluated either by simulations for the multicell systems of limited size or based on the formulas derived by asymptotic analysis. In this article, the asymptotic spectral-efficiency (ASE) of multicell systems with various BS cooperation and MUD schemes is derived based on the asymptotic analysis of the channel autocorrelation matrix’s eigenvalue distribution or of the signal-to-interference-plus-noise ratio (SINR) attained by a concerned scheme. The impacts of system load, signal-to-noise ratio (SNR) and intercell interference strength on the spectral-efficiency are demonstrated. Our studies and performance results show that, when taking into account of the trade-off between complexity and performance, the MMSE-SIC supported by data exchange among BSs may constitute a promising multicell processing (MCP) scheme that is beneficial for implementation in practical systems.

Cell Edge Capacity Improvement by Using Adaptive Base Station Cooperation in Cellular Networks with Fractional Frequency Reuse

The present paper focuses on the application of the base station cooperation (BSC) technique in fractional frequency reuse (FFR) networks. Fractional frequency reuse is considered to be a promising scheme for avoiding the inter-cell interference problem in OFDMA cellular systems, such as WiMAX, in which the edge mobile stations (MSs) of adjacent cells use different subchannels for separate transmission. However, the problem of FFR is that the cell edge spectral efficiency (SE) is much lower than that of the cell center. The BSC technique, in which adjacent BSs perform cooperative transmission for one cell edge MS with the same channel, may improve the cell edge SE. However, since more BSs transmit signals for one cell edge MS, the use of BSC can also increase the inter-cell interference, which might degrade the network performance. In this paper, with a focus on this tradeoff, we propose an adaptive BSC scheme in which BSC is only performed for the cell edge MSs that can achieve a significant capacity increase with only a slight increase in inter-cell interference. Moreover, a channel reallocation scheme is proposed in order to further improve the performance of the adaptive BSC scheme. The simulation results reveal that, compared to the conventional FFR scheme, the proposed schemes are effective for improving the performance of FFR networks.