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For multiple-input multiple-output (MIMO) wireless communication system with minimum mean square error (MMSE) detection, power allocation between pilot and data symbols is investigated under MMSE channel estimation in this paper. We first propose a novel soft-output MMSE MIMO detector by taking the channel estimation error into consideration. Then, by random matrix theorem, we propose an effective...
In this paper, we propose a double space-time transmit diversity (DSTTD)-based two-path relay system with power allocation and link combining methods. The two-path relaying protocol can restore spectral efficiency decreased due to the half-duplexing at the relay nodes and the DSTTD method can appropriately achieve the diversity gain from the two paths. To circumvent severe performance degradation...
Amplify-and-forward (AF) is one of the most popular and simple approaches to transmit information over a cooperative multi-input multi-output (MIMO) relay channel. In this paper, we propose three novel power allocation methods for the downlink of cooperative multi-user MIMO AF system, which are designed to maximize the weighted sum-rate (WSR) of the cooperative system, by considering two different...
Opportunistic scheduling for wireless network coding (OWNC) combines the strategies of opportunistic scheduling and network coding. This paper applies two variants of OWNC on a two-user OFDMA system. Symbol-based OWNC decides a strategy from sum rate of the whole OFDM symbol. Subcarrier-based OWNC decides a strategy from the capacity on a subcarrier level. Novel algorithms are derived for power allocation...
In wireless networks, designing transmission schemes adapting to time varying channel conditions is key to achieve better spectral efficiency. The design of such schemes for multi-hop wireless networks requires coordination among nodes in the network, which is achieved through feedback between nodes. Spectral efficiency can be improved for such networks by designing transmission schemes with limited...
We study a cognitive channel reuse approach for autonomous femtocell deployment in an OFDMA-based cellular network. The objective is to manage the uplink interference from macrocell users to femtocell access points. Macrocell users are normally far away from the base station and may cause strong uplink interference to the close-by femtocells. By cognitive interference recognition, a femtocell access...
We consider a power allocation problem for three-node cooperative diversity systems using a relay node. Specifically, we focus on an amplify-and-forward (AF) protocol due to the simple operation at the relay node which makes the mathematical analysis tractable. This protocol consists of two phases. The source transmits the signal to both relay and destination in the first phase. In the second phase,...
The next generation of cellular networks (Long Term Evolution) uses SC-FDMA (Single Carrier Frequency Division Multiple Access) on the uplink. In SC-FDMA, the uplink resources assigned to a user are called Resource Blocks (RBs) each of which consists of a set of consecutive subcarriers spanning all symbols available for data. Since at most one User Equipment (UE) is assigned to each RB then uplink...
We consider two different users sharing the same spectrum resource, interfering with each other, under outage performance requirements for both the users. We derive a practical condition to enable the spectrum-sharing under simultaneous outage performance. Furthermore, when the condition is fulfilled, we provide equations to define the two-dimensional region of allocated powers (P1, P2), for the two...
MIMO two-way relay is a well known method for realizing highly efficient multi-hop relay networks. Previous works in MIMO two-way relay network have focused on an equidistant topology of the relay nodes. However such a topology rarely exists in a practical situation. In a non-equidistant topology, the end-to-end network capacity degrades severely due to the bottleneck link caused by uneven SNR. Furthermore,...
Adaptive modulation and power allocation schemes have been widely used in multiple-input multiple-output (MIMO) systems to enhance spectral efficiency while maintaining bit error ratio (BER) to a target level. We derive the spectral efficiency of orthogonal space-time block codes (OSTBC) that can be achieved by applying adaptive modulation and power allocation. Compared to non-adaptive power scheme,...
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