Di Pang

Subcarrier Allocation for Multicast Services in Multicarrier Wireless Systems with QoS Guarantees

The throughput of conventional multicast transmission in wireless systems is limited by the user with the worst channel quality in the multicast service group. The subcarrier allocation for multicast services in multicarrier systems is a feasible solution to overcome the capacity limitation by exploiting the frequency diversity among subcarriers. However, most of the current subcarrier allocation algorithms are limited to unicast services. In this paper, we propose an optimal subcarrier allocation algorithm for multicast services with Quality of Services (QoS) guarantees. A low-complexity suboptimal algorithm is also proposed, which includes three steps: Conservative Allocation, Greedy Step and Iterative Enhancement. Simulation results show that the proposed algorithms significantly outperform the conventional multicast transmission scheme while at the same time guaranteeing the minimum data rates of all users. Moreover, simulation results also show that the performance difference between the optimal and suboptimal algorithms is small.

Contention region allocation optimization in ieee 802.16 ofdma systems

The random access scheme is used for initial and periodic ranging in the IEEE 802.16 protocol. The number of contention slots in the uplink subframe decides the system performance. However, how many contention slots should be allocated for ranging is not standardized in the protocol, so it is still necessary to determine the optimal number of contention slots. In this paper, the exact equations of the optimal numbers of initial ranging slots and periodic ranging slots are derived. An optimal dynamic allocator is also proposed to optimize the allocation of the initial and periodic ranging regions in the uplink subframe. The simulation results show that good system performance can be achieved with the optimal dynamic allocator.

A Distributed QoS Provision Scheme in IEEE802.16 Mesh Networks with Directional Antennas

QoS provisioning in wireless mesh networks has been to known as a challenging issue. In a distributed scheduling based wireless mesh backhaul network, conventional connection-based QoS provision mechanism requires considerable amount of overhead for per-link QoS signaling, thus cannot support high speed real time traffic. In this paper,we propose a DiffServ-like QoS provision mechanism for IEEE 802.16 mesh networks with directional antennas to increase network capacity and enable real time traffic. We develop a distributed scheduling algorithm based on our proposed scheme. Simulation results demonstrate that directional antennas can achieve higher network capacity compared with omni-antennas, and our QoS scheme can effectively guarantee QoS requirements of real time traffic.

Downlink Scheduling for QoS-Guaranteed Services in Multi-User MIMO Systems with Limited Feedback

Significant throughput gains and system fairness can be obtained by employing scheduling schemes based on precoding techniques. However, QoS guarantee requirements are seldom taken into account. In this paper, we propose a downlink scheduling algorithm for QoS-guaranteed services in multi-user multiple-input multiple-output (MIMO) systems with limited feedback. The proposed algorithm combines stream selection with multi-user packet scheduling. To maximize the overall capacity and reduce co-channel interference, streams are selected in accordance with precoding matrices. In multi-user packet scheduling, the base station first determines the SDMA region size for the primary streams. In addition, packet scheduling for the secondary streams is performed to completely exploit spatial multiplexing gains. Numerical results show that, at the cost of slightly lower system fairness, the proposed algorithm can achieve higher spectrum efficiency, and have a noticeable improvement in guaranteeing QoS requirements in terms of data rates and delay.

An Uplink Resource Allocation Scheme for SDMA-Based IEEE 802.16 MIMO-OFDMA Systems

In this paper, a low-complexity SDMA-based greedy resource allocation (SGRA) algorithm is proposed for the uplink of IEEE 802.16 MIMO-OFDMA systems taking into account co-channel interference. The objective of SGRA is to allocate resources in the space-time-frequency domain in order to maximize system throughput while guaranteeing QoS requirements of real time services. By performing efficient interference management, SGRA can be carried out in two phases. In the first phase, greedy resource allocation, primarily involving uplink scheduling and subchannel allocation across the MAC and PHY layers, is performed in the time-frequency domain. In the second phase, the resource allocation is extended to the space-time-frequency domain. Simulation results show that SGRA can improve system throughput while at the same time guaranteeing the delay and minimum data rate requirements of users.

Capacity optimization with stream control for MIMO Mesh networks

In this paper, we focus on the joint stream control and scheduling algorithm based on Multiple Input Multiple Output (MIMO) technique which can significantly improve network capacity without additional increase of bandwidth or transmit power. We propose a stream control algorithm to maximize the network capacity and develop a universal framework for capacity evaluation for MIMO Mesh networks. Simulation results demonstrate that our stream control algorithm can achieve higher network capacity compared with non-stream control.

A Region-Based Downlink Scheduling Algorithm in MIMO Precoding Systems

Although significant throughput gains and system fairness can be obtained by slot-based scheduling algorithms, the corresponding complexities are considerable. In this paper, we propose a region-based downlink scheduling algorithm for QoS-guaranteed services in multi-user multiple-input multiple-output (MIMO) precoding systems. In contrast with conventional slot-based scheduling, region-based scheduling allocates bandwidth based on resource regions consisting of several slots. The proposed algorithm combines QoS-urgent-degree and the proportional fairness to select candidate connections, and determines the size of each SDMA region. In addition, multi-user scheduling is performed in all SDMA regions to completely exploit spatial multiplexing gains. Simulation results show that, at the cost of slightly lower spectrum efficiency and data rate guarantee, the proposed region-based scheduling algorithm has much lower complexity, while at the same time it can achieve higher performances in system fairness and delay guarantee.

Optimizing initial ranging region allocation in IEEE 802.16 OFDMA systems

The IEEE 802.16 standard has been developed for metropolitan broadband wireless access systems. As part of the standard, the random access scheme is used for initial ranging. The ratio between the numbers of initial ranging slots and data slots in the uplink subframe decides the contention throughput, access delay and data throughput. However, no specific ratio is standardized in the protocol, so it is still necessary to determine the optimal number of initial ranging slots which is the decisive factor of the ratio. In this paper, we analyze the three parameters above, contention throughput, access delay and data throughput, each of which can be expressed as a function of the number of initial ranging slots. In addition, we define an objective function and derive the exact equation of the optimal number of ranging slots. Based on the equation, we propose an optimal dynamic controller to allocate the initial ranging region in the uplink subframe. We also propose an estimation scheme to obtain the number of contention users using Newton Iteration method. To verify the correctness of the analysis and the efficiency of the controller, we conduct extensive simulations. The simulation and analytical results match very well. The results show that good system performance can be achieved with the optimal dynamic controller.