Coordinated Multi-point Transmission/reception Research Articles

High-Mobility CoMP Massive MIMO Uplink Transmissions: Channel PSD Analysis and Doppler Spread Suppression

Coordinated Multi-Point transmission/reception (CoMP) is one of the promising techniques for high-mobility wireless communications systems to increase cell edge user throughput in both uplink and downlink transmission. In this paper, we consider the high-mobility CoMP uplink transmission, where a high-speed terminal (HST) simultaneously transmits signals to multiple base stations (BSs) with angle-domain Doppler shifts compensation. We derive the exact channel power spectrum density (PSD) for uplink CoMP transmissions. The antenna weighting technique is then proposed to suppress the Doppler spread, where an optimization problem is formulated to minimize the maximum Doppler spread among all the BSs. Numerical results are provided to corroborate both the PSD analysis and the superiority of antenna weighting technique.

Spectrum efficiency sub-carrier and energy efficiency power allocation for downlink multi-user CoMP in multi-cell system

Coordinated multi-point transmission/reception (CoMP) was proposed currently as an effective technology to improve cell-edge throughput in next-generation wireless systems. Most of the existing work discussed clustering methods mostly to maximize the edge user throughput while neglecting the problem of energy efficiency, such as those algorithm clustering base stations (BSs) of better channel condition and BSs of worse channel condition together. In addition, BSs usually increase the transmit power to achieve higher throughput without any considering of interference caused to other users, that may result in energy waste. The authors focus on the throughput maximizing problem while fully considering energy saving problem in CoMP systems. A coefficient is defined to describe the fitness of clusters. Then a sub-carrier allocation algorithm with clustering method is put forward for CoMP downlink, which can save the transmit power of BS and increase the throughput. Furthermore a power allocation scheme is proposed based on non-cooperation game; in which the transmit power is decreased by BSs generally to reach the Nash equation (NE). Simulation shows that the proposed sub-carrier allocation scheme and power allocation algorithm are better than the existing ones on users’ throughput while consumes much less energy.

Inter-cell Interference Mitigation in Multi-cell Cooperating System Based on SLNR Method

Coordinated Multi-Point transmission/reception (CoMP) can increase the performance of the cell edge users, the spectrum efficiency and mitigate the inter-cell interference among cells. In the CoMP scenario, several base stations which usually need satisfy the cooperating condition serve a single or several cell-edge users cooperatively. As we know, the CoMP techniques can be characterized into many classes. For the joint transmission system which is a classical CoMP system, a large number of data sharing and channel information exchange will be needed, where the system inevitably become comparatively complex. However, in this paper, the coordinated beam forming system will be considered, where several base stations cope with the inter-cell interference among cells, and all the base stations will only exchange the channel information. Further, the downlink multi-cell coordinated beam forming system is considered in this paper. In this downlink multi-cell coordinated beam forming system, it is crucial to design appropriate pre-coding schemes that are able to mitigate the inter-cell interference. In obtainable pre-coding schemes, the Signal-to-leakage-and-noise ratio (SLNR) pre-coding scheme is a promising pre-coding scheme in downlink multi-cell coordinated beam forming system, which makes closed-form solution accessible. Moreover, the problem in designing the pre-coding vectors is not a coupled problem since the cooperative base stations need not optimize the pre-coding vectors jointly, which are responsible for their own design of pre-coding vectors, that is, they will just carry out independent optimization. In this paper, we proposed a novel pre-coding scheme based on the SLNR scheme, which will determine the pre-coding vectors via iteration. The simulation results show that, the proposed method outperforms the conventional SLNR pre-coding scheme in bit error rate performance.

Inter-cell spectrum efficiency improvement technology

Improvement in inter-cell spectrum efficiency is a valuable research topic in mobile communication system, which affects cell edge user experience especially. According to current research results, there are three methods to deal with inter-cell interference to improve inter-cell spectrum efficiency, including inter-cell interference randomization, inter-cell interference cancellation and inter-cell interference coordination. This paper analyzes three important inter-cell spectrum efficiency improvement technologies, soft frequency reuse (SFR), uplink power control, and downlink coordinated multi-point transmission/reception (CoMP), and relative research progress.

Mobile Backhaul Optical Access Networks for Coordinated Multipoint Transmission/Reception (CoMP) Techniques in Future Cellular Systems

SUMMARY This paper describes mobile backhaul optical access network designs for future cellular systems, in particular, for those systems that exploit coordinated multipoints (CoMP) transmission/reception techniques. Wavelength-division-multiplexing passive optical networks (WDM-PON) are primarily considered and two proposals to enhance mobile backhaul capability of WDM-PONs for CoMP are presented. One is physical X2 links that support dedicated low latency and high capacity data exchange between base stations (BSs). The other is multicasting in WDM-PONs. It effectively reduces data/control transmission time from central node to multiple BSs joining CoMP. Evaluation results verify that the proposed X2 links and the multicasting enable more BSs to join CoMP

Cooperative Wireless Cellular Systems: An Information-Theoretic View

In this monograph, the impact of cooperation on the performance of wireless cellular systems is studied from an information-theoretic standpoint, focusing on simple formulations typically referred to as Wynertype models. Following ongoing research and standardization efforts, the text covers two main classes of cooperation strategies. The first class is cooperation at the base station (BS) level, which is also known as Multi-Cell Processing (MCP), network Multiple-Input MultipleOutput (MIMO), or Coordinated Multi-Point transmission/reception (CoMP). With MCP, cooperative decoding, for the uplink, or encoding, for the downlink, is enabled at the BSs. MCP is made possible by the presence of an architecture of, typically wired, backhaul links connecting individual BSs to a central processor (CP) or to one another. The second class of cooperative strategies allows cooperation in the form of relaying for conveying data between Mobile Stations (MSs) and BSs in either the uplink or the downlink. Relaying can be enabled by two possible architectures. A first option is to deploy dedicated Relay Stations (RSs) that are tasked with forwarding uplink or downlink traffic. The second option is for the MSs to act as RSs for other MSs. MCP is first studied under ideal conditions on the backhaul links, namely by assuming that all BSs are connected to a CP with unlimitedcapacity links. Both Gaussian (nonfading) and flat-fading channels are analyzed, for the uplink and the downlink, and analytical insights are drawn into the performance advantages of MCP in different relevant operating regimes. Performance comparison is performed with standard Single-Cell Processing (SCP) techniques, whereby each BS decodes, in the uplink, or encodes, in the downlink, independently, as implemented with different spatial reuse factors. Then, practical constraints on the backhaul architecture enabling MCP are introduced. Specifically, three common settings are studied. In the first, all the BSs are connected to a CP via finite-capacity links. In the second, only BSs in adjacent cells are connected via (finite-capacity) backhaul links. In the third, only a subset of BSs is connected to a CP for joint encoding/decoding (clustered cooperation). Achievable rates for the three settings are studied and compared for both the uplink and the downlink. The performance advantages of relaying are analyzed for cellular systems with dedicated RSs and with cooperative MSs. Different techniques are reviewed that require varying degrees of information about system parameters at the MSs, RSs, and BSs. Performance is investigated with both MCP and SCP, revealing a profound interplay between cooperation at the BS level and relaying. Finally, various open problems are pointed out.