Sok-Hyong Kim

Rate-Based Channel Assignment Algorithm for Multi-Channel Multi-Rate Wireless Mesh Networks

Wireless Mesh Networks (WMNs) support the cost-effective broadband access for Internet users. Although todays IEEE 802.11 PHY and MAC specifications provide multi-channel and multi-rate capabilities, exploiting available channels and data rates is a critical issue to guarantee high network performance. In multi-rate wireless networks, high-rate links heavily suffer from performance degradation due to the presence of low-rate links. This problem is often referred to as performance anomaly. In this paper, we propose a Rate-Based Channel Assignment (RB-CA) algorithm to alleviate performance anomaly in multi-channel multi-rate WMNs. By exploiting multiple channels, the proposed algorithm alters a low-rate single-hop path to a high-rate multi-hop path. With RB-CA, a large volume of traffics in WMNs can be simultaneously delivered from or to the Internet via multiple non-overlapping channels as well as high-rate links. Extensive ns-2 simulation experiments have been performed to evaluate the performance of RB-CA and compared it with the existing WMN architecture. Our simulation results show that RB-CA outperforms existing scheme in terms of packet delivery ratio and end-to-end delay.

A Cooperative Channel Assignment protocol for multi-channel multi-rate wireless mesh networks

Wireless mesh networks (WMNs) are considered as one of the outstanding technologies that provide cost-effective broadband Internet accesses to users. The off-the-shelf IEEE 802.11 PHY and MAC specifications support both multi-channel and multi-rate capabilities. However, designing an efficient channel assignment protocol that exploits both available channels and data rates is a critical issue to overcome the network performance degradation. In multi-rate wireless networks, high-rate links may severely suffer from throughput degradation due to the presence of low-rate links. This problem is often referred to as performance anomaly. In this paper, we design a Cooperative Channel Assignment (CoCA) protocol to consider the performance anomaly problem in multi-channel multi-rate WMNs. Based on the proposed family architecture, CoCA exploits the Estimated Delivery Time (EDT) metric and an efficient balancing algorithm. Using the EDT metric, CoCA performs channel assignments to form Multi-channel Multi-hop Paths (MMPs) so that CoCA separates high-rate links from low-rate links over different channels and increases the channel diversity. In addition, CoCA considers the performance anomaly problem and throughput fairness during channel assignments by utilizing the balancing algorithm. We evaluated the performance of CoCA through extensive simulations and found that CoCA outperforms existing well-known channel assignment protocols for WMNs.

A distributed channel assignment protocol for rate separation in wireless mesh networks

Wireless Mesh Networks (WMNs) support the cost-effective broadband access for Internet users. Although todays IEEE 802.11 PHY and MAC specifications provide multi-channel and multi-rate capabilities, exploiting available channels and data rates is a critical issue to guarantee high network performance. In multi-rate wireless networks, high-rate links heavily suffer from performance degradation due to the presence of low-rate links. This problem is often referred to as performance anomaly. In this paper, we propose a Rate-Based Channel Assignment (RB-CA) protocol to alleviate performance anomaly by using multiple channels in WMNs. RB-CA exploits a new metric, called Prioritized Transmission Time (PTT), in order to form High-rate Multi-channel Paths (HMPs). With HMPs, a large volume of traffics can be simultaneously delivered from or to the Internet via multiple non-overlapping channels as well as high-rate links. Extensive ns-2 simulations and experiments in a real test-bed have been performed to evaluate the performance of RB-CA and then we compared it with a well-known existing WMN architecture. Our simulation and experimental results show that RB-CA achieves improved performance in terms of aggregate throughput, packet delivery ratio, end-to-end delay, and fairness.

Local Channel Information Assisted Channel Assignment for Multi-Channel Wireless Mesh Networks

Wireless Mesh Networks (WMNs) has recently evolved into a hot issue to support high network capacity in wireless access networks. Although IEEE 802.11 PHY and MAC specification support up to 3 and 12 multiple non-overlapping channels according to IEEE 802.11b/g and IEEE 802.11a, respectively, it is a critical issue to exploit all channels to accommodate a large volume of network traffics in WMN. In this paper, we proposed a channel assignment scheme using the local channel information for multi-channel WMNs. In the proposed scheme, nodes perform only channel switching without channel scanning during data communication with neighbors operating on different channels. Our simulation study results show that the proposed scheme achieves improved throughput performance over existing schemes.

A survey and comparison of multichannel protocols for performance anomaly mitigation in IEEE 802.11wireless networks

SUMMARY Providing multichannel functionality can improve the performance of wireless networks. Although off-the-shelf IEEE 802.11 physical layer and medium access control specifications support multiple channels and multiple data rates, one of the major challenges is how to efficiently utilize available channels and data rates to improve network performance. In multirate networks, low-rate links severely degrade the capacity of high-rate links, which is known as performance anomaly. To overcome the performance anomaly problem, different data rate links can get equal air-time by exploiting time diversity and frequency diversity, or they can be separated over nonoverlapping channels. In this paper, we study existing multichannel protocols proposed to mitigate the performance anomaly problem by classifying them into single-radio protocols, multiradio single-hop protocols, and multiradio multihop protocols. To investigate the effectiveness of multichannel solutions for performance anomaly, we compare these protocols with well-known multichannel protocols that do not consider performance anomaly. In addition, this paper gives insightful research issues to design multichannel protocols that mitigate performance anomaly in IEEE 802.11 wireless networks. Copyright

System integration of GPSR and ADS-B for aeronautical ad hoc networks

The aeronautical ad hoc network (AANET) is a new type of ad hoc network consists of aircrafts in the airspace. AANETs can provide increased connectivity between ground control facilities and aircrafts, enable data communications, and act as the backup system when other systems fail. Greedy perimeter stateless routing (GPSR) is a position-based routing protocol and it shows great performance in ad hoc networks. However, the beaconing scheme of GPSR increases the control packet overhead and collision probability. Furthermore, there are connection problem and tracking problem in the location service of GPSR. In this paper, we propose a system integration scheme of GPSR and automatic dependent surveillance-broadcast (ADS-B). The proposed scheme eliminates the beaconing scheme and alleviates the problems in the location server by using the ground control facilities as the location server. We performed simulation studies, and our simulation results show that the proposed scheme significantly reduces the control packet overhead and collision probability.

A group-based channel assignment protocol for rate separation in IEEE 802.11-based multi-radio multi-rate ad hoc networks

Abstract Today’s IEEE 802.11 devices support multiple channels and data rates. Utilizing multiple channels and data rates can increase the performance of IEEE 802.11 networks. However, the multi-channel design to exploit available channels is one of the challenging issues. Moreover, performance anomaly occurs in IEEE 802.11 multi-rate networks when high-rate and low-rate links share a common channel, which degrades the overall network capacity significantly. In this paper, we introduce an extension of conflict graph, called rate conflict graph (RCG), to understand the performance anomaly problem in IEEE 802.11 multi-rate networks. Then, we propose a group-based channel assignment (GCA) protocol for IEEE 802.11-based multi-radio multi-rate single-hop ad hoc networks. In GCA, each node is equipped with multiple IEEE 802.11 interfaces, and links are subdivided into multiple groups, called component groups, by obeying the interface constraints. Then, GCA utilizes RCG and a heuristic algorithm to separate different data rate links via multiple channels so that the performance anomaly problem is addressed. Our extensive simulation results reveal that GCA achieves improved performance over existing channel assignment protocols designed to consider performance anomaly.

Distributing Data Rate Using Cooperative Channel Assignment for Multi-Rate Wireless Mesh Networks

Wireless Mesh Networks (WMNs) have emerged to provide cost-effective broadband Internet accesses. Todays IEEE 802.11 PHY and MAC specifications support multi-channel and multi-rate capabilities. Designing an efficient channel assignment protocol utilizing available channels and data rates is a hot issue to leverage the network capacity. In multi-rate networks, low-rate links severely decrease the capacity of high-rate links, known as performance anomaly. In this paper, we design a Cooperative Channel Assignment (CoCA) protocol to address the performance anomaly in WMNs. For the channel assignment of family architecture, CoCA utilizes the Estimated Delivery Time (EDT) metric and the balancing algorithm. With the EDT metric, CoCA separates different rate links via multiple channels. By using the balancing algorithm, CoCA also increases throughput fairness. Our simulation results show that CoCA outperforms the existing well-known channel assignment protocols for WMNs.

Channel Heterogeneity Aware Channel Assignment for IEEE 802.11 Multi-Radio Multi-Rate Wireless Networks

IEEE 802.11 devices are widely used, and terminals can be equipped with multiple IEEE 802.11 interfaces as low-cost IEEE 802.11 devices are deployed. The off-the-shelf IEEE 802.11 devices provide multiple channels and multiple data rates. In practical multi-channel networks, since there is channel heterogeneity which indicates that channels have different signal characteristics for the same node, channels should be efficiently assigned to improve network capacity. In addition, in multi-rate networks, low-rate links severely degrade the performance of high-rate links on the same channel, which is known as performance anomaly. Therefore, in this paper, we propose a heterogeneity aware channel assignment (HACA) algorithm that improves network performance by reflecting channel heterogeneity and performance anomaly. Through NS-2 simulations, we validate that the HACA algorithm shows improved performance compared with existing channel assignment algorithms that do not reflect channel heterogeneity.

Exploiting multiple channels for rate separation in IEEE 802.11 multi-radio wireless mesh networks

Wireless mesh networks (WMNs) have received an increasing interest for broadband Internet accesses. Todays IEEE 802.11 PHY and MAC standards offer multiple channels and data rates. One of challenging issues in WMNs is to exploit multiple channels and data rates for high performance WMNs. Channel assignments control the trade-off between node connectivity and channel diversity. In multi-rate WMNs, low-rate links severely affect the capacity of high-rate links, known as rate anomaly. In this paper, we propose a distributed family-based channel assignment (FCA) protocol to separate different data rate links using multiple channels so that rate anomaly is mitigated. FCA assigns channels for rate separation and improves node connectivity and channel diversity of WMNs by using a new channel assignment and routing metric and heuristic algorithms. Simulation and experiment results verify the potential of FCA for IEEE 802.11 multi-radio WMNs.