Dedicated Relay Stations Research Articles

Four-Way Relaying in Wireless Cellular Systems

Two-way relaying in wireless systems has initiated a large research effort during the past few years. Nevertheless, it represents only a specific traffic pattern and it is of interest to investigate other traffic patterns where such a simultaneous processing of information flows can bring performance advantage. In this paper we consider a four-way relaying scenario, where each of the two Mobile Stations (MSs) has a two-way connection to the same Base Station (BS), while each connection is through a dedicated Relay Station (RS). The RSs are placed in such a way that one RS and the terminals associated with it do not interfere with the other RS, and vice versa. We introduce and analyze a two-phase transmission scheme to serve the four-way traffic pattern defined in this scenario. Each phase consists of combined broadcast and multiple access. We analyze the achievable rate region of the new scheme for Decode-and-Forward (DF) operational model for the RS. We compare the performance with a state-of-the-art reference scheme, based on two-way relaying with DF. The results indicate that the achievable rate regions are significantly enlarged for the new scheme.

Erratum to: Performance Analysis on Two-Way Relay System with Co-Channel Interference

The second paragraph in Sect. 5 should read as follows: The fixation of interferer set does not impact the rationality of our analysis. Outage performance is shown in Fig. 2 with transmission power varying from 0 to 40 dB, to verify the effectiveness of analytic bounds. Lower and upper bounds of outage are separately displayed for c = 4 and c = 1/4 cases, representing dedicated relay station and user cooperation scenarios, respectively. For the 2TS and 3TS 2-hop schemes, we plot exact bounds as well as asymptotic lines, and they are shown to converge well from medium SINR regime, i.e., about PS = 15 dB for the large c case, and 20 dB for the small c case, in which the relay power is relatively low, and the asymptotic regime starts at a high point of power as a result. Diversity gain obtained from MRC in 3TS scheme is also revealed since the outage bounds decline with a greater slope. Only the asymptotic solutions are provided for the 3TS MRC scheme.

Outage Performance of Cooperative Relaying with Fixed and Best-Selected Mobile Relays Over Non-Identically Distributed Links

In multi-relay cooperative networks, selecting the best relay to cooperate is known to be spectrally efficient, provided that perfect channel state information (CSI) is available for relay selection. When relays are mobile, the time-varying nature of fading channels renders the provision of accurate CSI challenging and significantly degrades the performance of best relay selection. In this paper, the joint deployment of dedicated relay station (DRS) and mobile relay stations (MRSs) is considered, whereby the MRS selected based on CSI and the stationary DRS simultaneously forward the overheard signal to the destination within the total power constraint. Closed-form expressions for exact and asymptotic outage probability over non-identically distributed links are derived, and comparisons with related schemes are conducted to demonstrate the merits of the proposed scheme.

Optimal Resource Allocation in Relay-Assisted Cellular Networks With Partial CSI

Emerging cellular networks are likely to handle users with heterogeneous quality of service requirements attending to the nature of their underlying service application, the quality of their wireless equipment, or even their contract terms. While sharing the same physical resources (power, bandwidth, transmission time), the utility they get from using them may be very different and arbitrage is needed to optimize the global operation of the network. In this respect, resource allocation strategies maximizing network utility under practical constraints are investigated in this paper. In particular, we focus on a cellular network with half-duplex, MIMO terminals and relaying infrastructure in the form of fixed and dedicated relay stations. Whereas orthogonal-frequency-division multiple access is assumed, it is seen as a frequency diversity enabler since path loss is the only channel state information (CSI) known at the transmitters, which is refreshed periodically. With this setup, the performance of a state-of-the art relay-assisted transmission protocol is characterized in terms of the ergodic achievable rates, for which novel concave lower bounds are developed. The use of these bounds allows us to derive two efficient algorithms computing resource allocations in polynomial time, which address the optimization of the uplink and downlink directions jointly. First, a global optimization algorithm providing one Pareto optimal solution maximizing network utility during the validity period of one CSI is studied, which acts as a performance upper bound. Second, a sequential optimization algorithm maximizing network utility frame by frame is considered as a simpler alternative. The performance of both schemes has been compared in practical scenarios, giving special attention to the performance-complexity and throughput-fairness tradeoffs.

Resource Sharing via Planed Relay for

We present an improved version of adaptive distributed cross-layer routing algorithm (ADCR) for hybrid wireless network with dedicated relay stations ( ) in this paper. A mobile terminal (MT) may borrow radio resources that are available thousands mile away via secure multihop RNs, where RNs are placed at pre-engineered locations in the network. In rural places such as mountain areas, an MT may also communicate with the core network, when intermediate MTs act as relay node with mobility. To address cross-layer network layers routing issues, the cascaded ADCR establishes routing paths across MTs, RNs, and cellular base stations (BSs) and provides appropriate quality of service (QoS). We verify the routing performance benefits of over other networks by intensive simulation.

Any Resource Sharing via HWN* Routing

In this paper we present an adaptive distributed cross-layer routing algorithm (ADCR) for hybrid wireless network with dedicated relay stations (HWN*). To support versatile multimedia communication for Mobile Terminals (MTs), the HWN* integrates a cellular network, an ad hoc network and fixed relay nodes (RNs). A MT may borrow cellular data channels that are available thousands mile away via secure multi-hop RNs, where RNs are placed at flexible locations in the network. The MT can also communicate with each other or access internet ubiquitously. We discuss cross media access and network layers routing issues. The ADCR establishes routing paths across RNs or cellular network while providing appropriate QoS (quality of service). Through simulation, we verify the routing performance benefits of HWN* over conventional cellular systems and other hybrid network frameworks. It is anticipated that the simulation results reported in this paper will serve as a guideline for research based on distributed source routing involving heterogeneous wireless technologies.