We provide an effective video multicast framework over time division multiple access (TDMA)-based wireless mesh networks (WMNs). Heterogeneous user demand is considered where each multicast receiver has its own video quality demand. In video multicasting, different relay nodes in the same multicast tree may have different transmission rates by utilizing scalable video coding (SVC). Considering this distinguishing characteristic of video multicasting, the proposed multicast framework provides effective multicast routing, scheduling, and rate allocation algorithms. The purpose of the multicast routing and scheduling is to obtain a minimum length schedule which satisfies given quality demands of receivers. If the schedule is not feasible even with its minimum length due to the limited number of time slots in the network, rate allocation algorithm adjusts the transmission rates of relay nodes to generate a feasible schedule. The algorithm is designed to maximize the minimum utility of multicast receivers. Simulation results show that the proposed multicast routing and scheduling algorithms outperform existing schemes in terms of schedule length. The minimum utility is improved up to 30 percent by the proposed rate allocation algorithm compared to the existing method.

Abstract Orthogonal frequency division multiple access (OFDMA) is considered as one of the technologies for 4th generation (4G) due to its robustness against multi‐path environment. OFDMA also has the advantage of flexibility in resource allocation, which cannot be supported by existing duplex schemes. In this paper, we propose dynamic hybrid duplex (DHD) which will enhance the efficiency and flexibility of the OFDMA system. To establish the framework of resource allocation for the DHD, we formulate DHD resource allocation problem (DRAP) which maximizes the total users' data rate with power, rate, and subcarrier allocation constraints. A heuristic procedure is developed to solve the problem. The procedure finds the best mode and the best amount of resources allocated to downlink (DL) and uplink (UL). Simulation is performed with five scenarios to evaluate the DHD. Its results show that the proposed DHD outperforms other duplex schemes in various environments. Copyright © 2010 John Wiley & Sons, Ltd.

With recent advances in wireless technology, the ability to use multiple transmission rates and multiple network interface cards (radios) in wireless networks has been widely recognized. In this paper, Multi-Rate and Multi-Radio (MR2) characteristics are exploited to reduce end-to-end transmission delay for reliable multicasts. To achieve this goal, a new routing metric, MR2_ETT, is introduced. It accounts for the link transmission time by considering the usable number of radios and the transmission rate on the link. This metric is used in a routing protocol that is also proposed in this work. The routing protocol, termed Multi-rate Multi-radio On-Demand Multicast Routing Protocol (MR2_ODMRP), makes ODMRP suitable for a MR2 environment. Simulation results show that MR2_ODMRP outperforms ODMRP in multi-rate or multi-radio wireless mesh networks.

Abstract Code division multiple access system with time division duplex (CDMA‐TDD) is a promising solution to cope with traffic asymmetry of downlink (DL) and uplink (UL) in multimedia services. When a rate of asymmetry is different in each cell, CDMA‐TDD system may employ crossed slots, where a timeslot is used for different links in cells. However, it may suffer from base station (BS)‐to‐BS and mobile station (MS)‐to‐MS interference problem. Zone division scheme is an efficient way to tackle the crossed slot interference by dividing a cell into inner and outer zones and restricting communication in crossed slots only to inner zone. In this paper, we propose distributed crossed slot resource allocation with zone division in multi‐cell CDMA‐TDD system. Two conditions for crossed slot resource allocation are defined and the bound on the size of inner zone is analyzed mathematically based on the conditions. Relationship between the capacity of crossed slot and the size of inner zone is also analyzed. Then, numerical results of the mathematical analysis are presented; showing that the proposed crossed slot allocation is effective for traffic asymmetry problem. Copyright © 2009 John Wiley & Sons, Ltd.

Mobile IPTV is a technology that enables users to transmit and receive multimedia traffic anywhere and anytime, using any device. However, in a wireless environment, the network capacity often does not reliably support high-quality high-bandwidth IPTV service traffic. In this paper, a novel resource allocation scheme for Qos-guaranteed mobile IPTV that considers the TV viewing behavior of the user is proposed. A heterogeneous MAC protocol is considered for the service in wireless mesh networks based on IEEE 802.11.

Abstract Bluetooth is an open specification for a technology to enable short‐range wireless communications that operate in an ad hoc fashion. Bluetooth uses frequency hopping with a slot length of 625 μs. Each slot corresponds to a packet and multi‐slot packets of three or five slots can be transmitted to enhance the transmission efficiency. However, the use of multi‐slot packet may degrade the transmission performance under high channel error probability. Thus, the length of multi‐slot should be adjusted according to the current channel condition. Segmentation and reassembly (SAR) operation of Bluetooth enables the adjustment of the length of multi‐slot. In this paper, we propose an efficient multi‐slot transmission scheme that adaptively determines the optimal length of slots of a packet according to the channel error probability. We first discuss the throughput of a Bluetooth connection as a function of the length of a multi‐slot and the channel error probability. A decision criteria which gives the optimal length of the multi‐slot is presented under the assumption that the channel error probability is known. For the implementation in the real Bluetooth system, the channel error probability is estimated with the maximum likelihood estimator (MLE). A simple decision rule for the optimal multi‐slot length is developed to maximize the throughput. Simulation experiment shows that the proposed decision rule for the multi‐slot transmission effectively provides the maximum throughput under any type of channel error correlation. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract Future wireless communication systems are expected to provide a broad range of multimedia services that have a significant traffic asymmetry between uplink and downlink. The code division multiple access‐time division duplex (CDMA‐TDD) system is a promising solution to cope with the problem of traffic asymmetry. However, the TDD system is subject to inter‐cell interference compared to frequency division duplex (FDD) system. Since both uplink and downlink share the same frequency in TDD, uplink and downlink may interfere each other especially when neighboring cells require different rates of traffic load. Thus, the resource allocation among cells is an important issue in TDD. In this paper, the resource allocation in the CDMA‐TDD is formulated as a mixed integer programming (MIP) problem. A dynamic resource allocation algorithm (DRAA) is provided that effectively solves the traffic asymmetry problem. The MIP problem is also solved by a well‐known branch and bound procedure. Both the crossed slot and non‐crossed slot allocation are examined and compared to the DRAA. Computational result shows that proposed DRAA gives a good performance as the traffic asymmetry increases between the uplink and downlink. Copyright © 2003 John Wiley & Sons, Ltd.