Hua-Chiang Yin

An Effective Path Selection Metric for IEEE 802.16-based Multi-hop Relay Networks

For usage models of coverage extension and throughput enhancement, a novel framework, Multi-hop Relay (MR) network, which consists of various kinds of stations such as the base station (MR-BS), the relay station (RS), and the mobile station (MS) is proposed by the study group under the IEEE 802.16 WG. With the help of RSs, data transmissions between MR-BS and MS become more reliable and effective. In the paper, we propose a new measurement, called effective radio resource index (ERRI), to indicate the effectiveness of radio resource of a link used to transmit data. The ERRI of a link is normalized and compared to the metric defined as the bandwidth unit required for transmitting a fixed amount of data using 64-QAM CC 5/6 with repetition 1. Additionally, a cost function of a relay path between MR-BS and MS is also proposed to efficiently facilitate the evaluation of path selection schemes for MR networks. Simulation results show that the relay path selection scheme with ERRI considerations is indeed effective in terms of network throughput.

Adaptive rate controller for mobile ad hoc networks

Mobile devices in the IEEE 802.11 wireless local area network (WLAN) have the ability to transmit data frames at one of four transmission rates 1Mb/s, 2Mb/s, 5.5Mb/s and 11Mb/s. This is because the commercial WLAN transceivers are equipped with several modulation schemes. According to the characteristics of the modulation scheme, a higher transmission rate will result in a smaller transmission range and longer time consumption on data frame transmission. If the channel environment is relatively clear and the transmission distance is short, one should choose a higher transmission rate for data transmission to maximise channel utilisation. On the contrary, a lower transmission rate should be selected to minimise the frame loss and frame error probabilities if the bit error rate is high. Therefore, the problem of choosing a proper transmission rate to accommodate a varying environment is a new and valuable problem in the wireless LANs. To our knowledge, it is very difficult and impractical to formalise an indoor environment since the channel status is quite unstable and unpredictable. Instead, we propose an adaptive rate controller (ARC), which employs the powerful fuzzy set function, for intelligently selecting the transmission rate for frame transmissions. This fuzzy control function refers the received signal strength indicator (RSSI), the frame error rate (FER) and the medium access control (MAC) delay to make a correct decision. Simulation results demonstrate that the proposed fuzzy controller indeed enhances the network throughput and the access delay.

Symmetric Path Selection in IEEE 802.16 Multi-Hop Relay Networks with Error Prone Links

Recently, the IEEE 802.16j task group has focused on the development of a novel network architecture with the aid of relaying technique for range extension, coverage extension and throughput enhancement. Our prior research, to select an optimal path in the IEEE 802.16 multi-hop relay (MR) network, proposes a novel metric, called ERRI, which indicates the effectiveness of radio resource of a link used to transmit data. Under the consideration of error-prone links due to unreliable channel conditions, the paper, on the basis of our previous work, models an error-prone MR network as a finite-state Markov chain, and then develops a new path cost function for symmetric path selection. Simulation results show that the relay path selection scheme with modified ERRI considerations significantly achieves throughput gains in the error-prone IEEE 802.16 MR network.

Virtual Direct Link Access for IEEE 802.16 Wireless Metropolitan Area Networks (WMANs)

Communication technology of broadband wireless access (BWA) system designed for wireless metropolitan area networks (WMANs) has become matured. The IEEE 802.16 standard has the potential to be the global standard for WMANs. In this paper, we first point out the inefficient data transmission in IEEE 802.16 point-to-multipoint network and then propose the virtual direct link access (VDLA) scheme which is based on smart scheduling strategy and location reporting protocol. The VDLA allows pairs of subscriber stations to communicate directly without passing through the base station. Simulation results show that the IEEE 802.16 WMANs with VDLA achieves higher average network throughout when handling Intranet traffic.

Smart handoff scheme for supporting roaming between WLAN and GPRS networks

Recent advancement in personal communication services (PCS) provides wireless multimedia services for users on the move. For establishing the convenient access environment, the evolution of IP-based integrated scheme becomes very urgent for public wireless access systems. In this paper, we clarify the well-known issues of integrating the general packet radio service (GPRS) network and IEEE 802.11 wireless local area network (WLAN). These issues include the inconsistence in transmission rate and coverage area, the difficulty in seamless handoff, the complexities of mobile IP and address translations, and so on. Based on classified cases, we propose the circular probe strategy (CPS) to measure the precise handoff latency of a mobile node roaming from one network to another. This information helps mobile nodes and its home agent (HA) to decide the appropriate handoff timing, to maximize the data transmission rate and to perform seamless handoff in the heterogeneous system.

Efficient Data Forwarding Schemes for IEEE 802.16j Multi-hop Relay Networks

In this paper, we propose two efficient schemes, named the CID-translated forwarding scheme (CTFS) and the enhanced CID-translated forwarding scheme (E-CTFS), to forward the broadcast data in the IEEE 802.16j multi-hop relay (MR) network. Motivated by the effective CID translation, CTFS and E-CTFS primarily relay the broadcast message without appending the relay MAC header. Moreover, E-CTFS classifies the content of the broadcast message, and then uses an efficient approach for message relay. The simulation results demonstrate that the proposed CTFS scheme occupies less resources and supports fewer number of MSs than the tunnel forwarding scheme proposed in the IEEE 802.16j draft. Furthermore, E-CTFS can achieve significant resource reduction and support larger number users than CTFS.

Efficient forwarding scheme for downlink broadcast messages in IEEE 802.16j multi-hop relay networks

Graphical AbstractDisplay Omitted We design two schemes for forwarding broadcast messages in IEEE 802.16 multi-hop relay networks.The proposed schemes consider a connection identifier (CID) translation strategy.We provide the analysis of the forwarding performance.Considering CID translation will reduce the amount of resources used.Considering CID translation will reduce the transmission latency. Although the IEEE 802.16j standard introduces a connection identifier (CID)-based forwarding scheme and a tunnel-based forwarding scheme, these schemes exhibit poor performance when forwarding broadcast messages. This study considers a CID translation strategy and proposes two CID-translated forwarding schemes for IEEE 802.16 multi-hop relay networks. The basic CID-translated forwarding scheme does not require to append the relay MAC header of the tunnel-based scheme to the broadcast messages. The enhanced CID-translated forwarding scheme further divides a broadcast message into a common part and a specific part and forwards these parts in a multicast manner and a broadcast manner, respectively. Simulation results validate that the basic CID-translated forwarding scheme uses fewer resources than the tunnel-based forwarding scheme. Moreover, the enhanced CID-translated forwarding scheme outperforms the basic CID-translated forwarding scheme in terms of the system resources used and transmission latency.