[show abstract][hide abstract] ABSTRACT: In Dense Wavelength Division Multiplexing (DWDM) technologies, the optimal packet scheduling issue is commonly encountered in multiple channel networks. NP-hard problems deal with finding a way to rearrange packets from multiple channels into a finite and rare channel. Genetic Algorithm (GA) is one of the most efficient ways to solve these issues. We hope to find a better solution to our task through the GA characteristics of multiprocessor searching and survival of the fittest. Therefore, a modified and achievable hardware architecture of GA is presented in this paper. This architecture can increase both the speed of packet scheduling and the efficiency of DWDM in Optical Communication Networks. way to solve this problem. It is concluded that crossover and mutation of chromosome and fitness function calcu- lation can converge faster and therefore allow an effi- cient way to find the optimal solution (6). In this paper, besides using the Matlab simulation software to prove the practicality and superiority of GA, we also presented an achievable hardware architecture in DWDM of optimal packet scheduling (1, 2, 3, 7, 8). This paper is organized as follows: Section 2 intro- duces the ways in which GA solves the optimal packet scheduling and presents the simulation results. Section 3 describes a hardware architecture designed for GA. Sec- tion 4 contains our conclusion.
Proceedings of the 2006 Joint Conference on Information Sciences, JCIS 2006, Kaohsiung, Taiwan, ROC, October 8-11, 2006; 01/2006
[show abstract][hide abstract] ABSTRACT: The infrastructure architecture of wireless local area networks (WLANs) has been widely established in many environments to provide convenient multimedia services. However, in this standard operation, arbitrary channel contention and frequent handshaking significantly affect data transmission efficiency between AP and stations (STAs). This paper proposes an ACK-based polling strategy (APS) to reduce the overheads of channel contention and frequent handshaking via adaptively arbitrating and scheduling the transmission sequence of STAs. That is, the proposed APS makes AP be able to defer the ACK frames replied to the STAs, which still have more data in their buffers, in order to temporarily terminate their subsequent contention accesses. A terminated STA is permitted to transmit data frame again only when it receives the ACK frame replied from AP. Using the ACK-based polling mechanism, the overheads of channel contention and frequent handshaking are reduced and the network goodput is improved. Using the ACK frames, the APS can be further enhanced to support the quality of service (QoS) for various multimedia applications. Simulation results demonstrate that the APS with enhanced QoS function is able to efficiently cope with various transmission requirements in multimedia WLANs.
[show abstract][hide abstract] ABSTRACT: In the backbone network, a Steiner multicast tree (SMT) will be established for multi-cast members to minimize the traffic load on networks. However, a communication link or node may fail due to some accidental factors during the transmission period. Down-stream nodes with respect to the failed link/node will be forced to leave this tree. In order to guarantee the quality of service (QoS), it is desirable to have some schemes for the multicast tree so that such termination of service can be avoided or at least, reduced. In this paper, we propose a fixed SMT algorithm (FSA) to construct the Steiner backup mul-ticast tree (SBMT). Based on FSA, for each 'critical' path, an alternate route with enough bandwidth will be reserved such that most fatal failures in the network can be recovered immediately. The way to determine critical paths is based on statistical analysis. In ad-dition, an adaptive SMT algorithm (ASA) is proposed to construct both SMT and SBMT on unreliable networks. The adjustment of the SBMT when nodes dynamically join or leave the SMT is also discussed. The degree of fault tolerance of the proposed strategies is evaluated and compared by simulation. Simulation results demonstrate that FSA and ASA improve the reliability in stable and unstable networks, respectively. Moreover, the dynamic joining process of a node will be sped up by taking both SMT and SBMT into considerations. Simulation results are presented to demonstrate the effectiveness of the optimization.
International Journal of Computers and Applications. 01/2006; 28(2).
[show abstract][hide abstract] ABSTRACT: This paper proposes efficient and fast retransmission (EFR) schemes for IEEE 802.11 multi-rate wireless networks. Without major modification of IEEE 802.11 standard, EFR provides immediate data transmission for both ad hoc wireless local area networks (WLAN) and infrastructure WLAN. Also, EFR can compensate for high frame error rates resulting from existing poor rate control algorithms. We develop an analytical model and a simulation model to investigate the performance of EFR. Our study indicates that in terms of average medium access control delay, average queuing delay, completion rate and average collision times per transmission. EFR outperforms standard IEEE 802.11 carrier sense multiple access/collision avoidance mechanism.
[show abstract][hide abstract] ABSTRACT: The medium access control (MAC) protocol defined in IEEE 802.15.4 standard is able to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). The modified CSMA/CA protocol used to minimize power consumption does not have the hidden-node protection mechanism, such as RST/CTS mechanism, for the sake of reducing the control overheads. Referring to previous research results, which proved that the probability of any two nodes in infrastructure network unheard each other is about 41%, the hidden-node problem (HNP) could result in inefficient data transmission in WPAN and quick power consumption. In this paper, we propose a simple and efficient grouping strategy to solve the IEEE 802.15.4 HNP without needing extra control overheads in data transmissions. The proposed strategy groups nodes according to their hidden-node relationships and then separates the periodic transmission period into several non-overlapping sub-periods, one for each group. The WPAN coordinator is responsible for detecting the hidden-node situation and performing the grouping procedure if necessary. In this paper, we also prove that the maximal number of groups in a WPAN is five. Simulation results demonstrate that the proposed strategy is able to improve the standard transmission efficiency and to conserve energy by eliminating the unnecessary collisions.
Wireless Internet, 2005. Proceedings. First International Conference on; 08/2005
[show abstract][hide abstract] ABSTRACT: All mobile stations (STAs) in IEEE 802.11 infrastructure wireless local area networks (IWLAN) are coordinated by an access point (AP). Within the 2.4 GHz unlicensed industry, science, and medicine (ISM) band defined in the IEEE 802.11 2.4 GHz physical layer (PHY) specifications, three channels are available for concurrently transferring data packets at the coverage area of an AP. In most of small/medium enterprises or home environments, an AP with one selected channel is sufficient for covering whole service area, but this implies that the radio resources for the remaining two channels are wasted. In order to overcome the drawback, we propose a new and simple media access control (MAC) protocol, named wireless switch protocol (WSP), for increasing the throughput of IEEE 802.11 IWLAN network to support high quality multimedia traffic. This is achieved by allowing any pair of STAs in IWLAN to exchange data packets in one of other idle channels after their handshake with each other in the common channel controlled by AP. Simulation results show that the total network throughput of WSP depends on the time taken by channel switching, and on the ‘Intranet’ and ‘Internet’ traffic distribution, where the Intranet and Internet mean data transmission between STAs in IWLAN and between the STA and wired host, respectively. When all data packets are Intranet traffic and the traffic load is heavy, the ratio of Goodput for the proposed WSP to that of IEEE 802.11 standard approximates 400%. In the worse case of all Internet traffic, the proposed WSP still obtains the similar throughput as that of IEEE 802.11 standard.
Mobile Networks and Applications 01/2005; 10:741-751. · 1.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: The key features of IEEE 802.15.4 wireless personal area network (WPAN) standard are the low data rate, short transmission distance, and low power consumption. The WPAN consisting of coordinator and device nodes is often established for monitoring the environmental information in a periodic fashion. The most critical issue of IEEE 802.15.4 WPAN is the capability of dealing with real-time or near real-time services, which require the limited latency and delay jitter. Two parameters, named as beacon order (BO) and superframe order (SO), are defined to control the superframe length as well as the active and inactive periods in superframe. However, using two parameters is very difficult to achieve deliver smooth and constant data stream from device nodes to coordinator. Although standard allots a portion of active period to be the guarantee time slots (GTS) for real-time services, the access interval of real-time frames is still affected by the assigned superframe length. Instead of using the inefficient GTS scheme, this paper proposes an adaptive interleaving access scheme (IAS) with a parameter interleaving order (IO) to adjust the superframe structure such that the active portion is spread over entire superframe in order to control the access latency as well as the bandwidth wastage. The simulation results demonstrate that the proposed IAS not only decreases average data renew interval (i.e. access latency) but also increases the battery lifetime of device nodes.
[show abstract][hide abstract] ABSTRACT: The IEEE 802.11 standard supports several independent and equal-capacity communication channels, which can be shared simultaneously and accessed by mobile stations in existing wireless local area networks (WLANs). However, under the restriction of one transceiver per network adapter, these mobile stations can only access one of these communication channels and, thus, the remainder channels are wasted inevitably. A multichannel carrier sense multiple access (CSMA) protocol, multichannel multiple access (MMA) protocol, is proposed in the paper for supporting parallel transmissions under the above single transceiver constraint. The MMA protocol enables mobile stations to contend for access of multiple data-transferring channels through the use of a dedicated service channel during each contention reservation interval (CRI). After granting the access right of these channels, these mobile stations can transmit data frames over different channels by using a pre-defined channel scheduling algorithm (CSA) in a distributed manner. The time complexity of the proposed heuristic CSA is O(|X|log|X|+|X|×M2) where |X| and M denote the number of successful requests in the CRI and the number of available channels, respectively. An improved MMA+ protocol with extending reserved transmission opportunities is also introduced and the goal is to maximize the channel utilization further. Simulation results show that the proposed MMA with CSA achieves a much higher throughput than conventional IEEE 802.11 WLAN with single channel. Simulation results also indicate that the achievable peek network throughput is not linearly proportional with the number of channels because of the native collision problem caused by single transceiver.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: In IEEE 802.11 infrastructure wireless local area networks (IWLANs), most of data frames are transmitted between access point (AP) and wireless stations (STAs). The data transmission in IWLAN is inefficiency since the excessive overhead generated from frequent handshakes between AP and STAs and contentions among STAs. For minimizing the bandwidth wastage, in this paper, we propose a new ACK-based polling strategy to efficiently coordinate and arbitrate the sequence of transmissions among STAs. The proposed strategy alters the consecutive handshake sequence between sender and receiver defined in IEEE 802.11 medium access control (MAC) protocol to minimize the handshaking overhead and to reduce or even eliminate the potential collisions in transmissions. Different from standard handshakes, the recipient of data frame postpones sending acknowledgement (ACK) control frame to schedule the timing of the next transmission from sender. The ACK frame is sent from receiver via standard contention protocol and the sender waits the ACK frame for the authorization to send the next data frame. The simulations and analytical results demonstrate that the proposed ACK-based contention strategy is able to improve the transmission efficiency by simply reducing the overheads of handshakes and collisions in the wireless networks.
Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
[show abstract][hide abstract] ABSTRACT: The hybrid fiber coax (HFC) technology enables the con-ventional cable-television (CATV) network to provide sub-scribers with Internet access services. In this paper, we propose a new preemptive priority scheme (PPS) for IEEE 802.14 hybrid fiber coax (HFC) networks with the intelli-gent nodes (INs). The INs are placed between the headend controller and stations. By using INs, that stand for down-stream subscribers to contend for the demand resources, the collision probability and the collision resolving period can be reduced . In this paper, we further extend such network architecture to support multi-priority access. In each IN or individual station, the proposed PPS will pre-vent a higher priority request from colliding with requests of lower priority. Moreover, in PPS, the granted bandwidth for lower priority requests can be preempted by the waiting request with higher priority. This will speedup the chan-nel capture by priority data. The efficiency of PPS is in-vestigated by simulations. Simulation results show that by adopting INs with PPS to be an agent for subscribers can not only shorten the collision resolving period but also min-imize the average request delay of priority data.
[show abstract][hide abstract] ABSTRACT: The IEEE 802.11 wireless local area networks (WLANs) standard supports several equal-capacity communication channels which can be simultaneously shared and accessed by mobile stations. In such multichannel communication system, a mobile station basically can transmit on any of these channels based on a suitable access control protocol. However, with the feature of one transceiver per mobile station, the standard restricts mobile stations to operate in one selected channel and the other channel capacities are wasted inevitably. In this paper, we propose a new carrier sense multiple access (CSMA) based protocol, called multichannel access protocol (MAP), to support parallel transmissions in IEEE 802.11 ad hoc WLANs. To realize the proposed MAP protocol over contemporary ad hoc WLANs, the MAP protocol is not only compliant with the IEEE 802.11 standard but also taking one transceiver constrain into consideration. All mobile stations with MAP will contend for channel access right in a dedicated channel during a periodical contention reservation interval (CRI) and then transmit data frames over different channels by a channel scheduling algorithm (CSA). Given a number of requests, the problem of finding a proper schedule for these requests to be served on a multichannel system so that the longest channel busy period is minimal is known to be NP-hard (Hou, et al. 1994). The time complexity of proposed heuristic CSA is O(|X| log |X| + |X|M<sup>2</sup>) where |X| and M denote the number of successful requests in the CRI and the number of available channels respectively. Simulation results show that the proposed MAP protocol with CSA achieves an obviously higher throughput than conventional IEEE 802.11 WLAN with single channel.
Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003. 14th IEEE Proceedings on; 10/2003
[show abstract][hide abstract] ABSTRACT: In IEEE 802.11 infrastructure wireless local area networks (WLAN), all mobile stations (STAs) are coordinated by an access point (AP), which is a static device and plays the role of the bridge between wired and wireless networks. Such coordination is achieved by restricting all STAs to access the channel listened by AP. Within the 2.4 GHz unlicensed industry, science, and medicine (ISM) band defined in the IEEE 802.11 2.4 GHz physical layer (PHY) specifications, three of fourteen channels, which are independent and exclusive, can be used to transfer data packets at a same area concurrently. However, in most small/medium enterprises or home environments, one AP is sufficient for covering whole service area. This implies that the other two channels' capacity has being wasted by the single channel operation defined in standard. In order to overcome the drawback, we propose a new and simple CSMA based media access control (MAC) protocol, named wireless switch protocol (WSP), for promoting the IEEE 802.11 aggregate network throughput. This is simply achieved by allowing any pair of STAs in WLAN to exchange data packets in another idle channel after their handshaking with each other in the common channel, which is specified by AP. Simulation results show that the total network throughput of WSP is obviously depending on the time taken by the changing frequency channel and the intranet and Internet traffic distribution, where the intranet and Internet mean the data exchanged between mobile STAs, and between STA and wired host, respectively. If all data packets are intranet traffic and the traffic load is heavy, the improving ratio of derived goodput of proposed WSP and that of the IEEE 802.11 standard approximates 400%. In the worse case that all traffic is Internet traffic, the proposed WSP still obtains the similar throughput as that of IEEE 802.11 standard.
Communications, 2003. ICC '03. IEEE International Conference on; 06/2003
[show abstract][hide abstract] ABSTRACT: The IEEE 802.11 standard and enhanced amendments have defined fourteen transmission rates (1/2/5.5/6/9/11/12/18/22/24/33/36/48/54 Mbit/s) for mobile stations to transmit and receive data frames. With the characteristic of modulation schemes, a higher level modulation scheme requires a higher signal-to-noise ratio (SNR) and, consequently, the data rate is inversely proportional with the transmission distance. Using a higher level modulation scheme, a higher network throughput can be expected; however, the frame error probability will also become higher. Doubtlessly, it is an open issue of selecting a proper modulation scheme for a pair of mobile stations in a time-varying indoor environment. This paper proposes a safe multiple access-rates transmission (SMART) scheme for enhancing the reliability of data transmission in the IEEE 802.11 multi-rate infrastructure wireless networks. The SMART scheme provides reliable transmission by reserving a retransmission period, which immediately follows the transmitted frame and is estimated from a lower transmission rate, for each transmitted frame. If any error occurs on the transmitted frame, the sender will retransmit it right away by using a lower transmission rate to make sure of successful retransmission. Otherwise, the reserved period will be taken by the access point (AP), which often has the longest waiting queue and is the bottleneck in infrastructure wireless networks. The efficiency of the proposed SMART scheme is evaluated by simulation. Simulation results show that the derived performance of the SMART scheme is significantly better than standard under the real environment with asymmetric traffic load.
Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on; 04/2003
[show abstract][hide abstract] ABSTRACT: In this paper, we present a data flushing data transfer (DFDT) protocol for IEEE 802.11 wireless ad hoc network. The basic mechanism of DFDT is quite the same as the distributed coordination function (DCF) of the medium access control (MAC) of IEEE 802.11, which uses a random access delay backoff time after a busy medium condition and RTS/CTS dialogue before sending actual payload data (direct data/ACK could also be used). The enhancement introduced by DFDT is mainly produced by the compilation process (CP), which fits as many MAC layer packets as possible into one physical layer packet within the limit of a predetermined length. By using the CP, we lower the protocol overhead, the packet arrival rate of the physical layer, and network contention all with one action. DFDT takes the advantages of the RTS/CTS mechanism but has less the overhead. Simulation results backed by numerical analysis show growing improvement in performance, limited by the saturation of the network, as the network load gets higher.
Wireless Communications and Networking, 2003. WCNC 2003. 2003 IEEE; 04/2003
[show abstract][hide abstract] ABSTRACT: Wireless technologies and applications received great attention in recent years. The medium access control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel in wireless local area networks (WLANs). The request-to-send/clear-to-send (RTSICTS) mechanism is an optional handshaking procedure used by the IEEE 802.11 wireless network to reduce the possibility of collision. The RTS-Threshold (RT) value which determines when the RTS/CTS handshaking mechanism should be used is an important parameter to investigate; since different RT values will produce different performance characteristics in data transmission. This paper presents an analysis of the influence of the RT parameter on the IEEE 802.11 wireless network, and gives a guideline to dynamically adjust the RT value. Simulation results of this paper show that the RTSICTS mechanism should be always turned on (RT = 0) to achieve an excellent performance while saving complex work designing a dynamic RT mechanism which will not have notable effect.
Parallel and Distributed Systems, 2002. Proceedings. Ninth International Conference on; 01/2003
[show abstract][hide abstract] ABSTRACT: This paper discusses the issue of routing packets over an IEEE 802.11 ad hoc wireless network with multiple data rates (1/2/5.5/11 Mb/s). With the characteristics of modulation schemes, the data rate of wireless network is inversely proportional with the transmission distance. The conventional shortest path of minimum-hops approach will be no longer suitable for the contemporary multi-rate/multi-range wireless networks (MR 2 WN). In this paper, we will propose an efficient delay-oriented multi-rate/multi-range routing protocol (MR 2 RP) for MR 2 WN to maximize the channel utilization as well as to minimize the network transfer delay from source to desti-nation. By analyzing the medium access delay of the IEEE 802.11 medium access control (MAC) protocol, the proposed MR 2 RP is capable of predicting the transfer delay of a routing path and finding the best one, which has the minimum transfer delay from source to destination. The proposed MR 2 RP may choose a longer path but with less contention competitors and buffer queuing delay. Simulation results show that MR 2 RP performs the load balancing and fast routing very well, and its call blocking probability is obviously lower than that of conventional minimum-hops approach with fixed transmission rate.
[show abstract][hide abstract] ABSTRACT: The dense wavelength division multiplexing (DWDM) technique has been developed to provide a tremendous number of wavelengths/channels
in an optical fiber. In the multi-channel networks, it has been a challenge to effectively schedule a given number of wavelengths
and variable-length packets into different wavelengths in order to achieve a maximal network throughput. This optimization
process has been considered as difficult as the job scheduling in multiprocessor scenario, which is well known as a NP-hard
problem. In current research, a heuristic method, genetic algorithms (GAs), is often employed to obtain the near-optimal solution
because of its convergent property. Unfortunately, the convergent speed of conventional GAs cannot meet the speed requirement
in high-speed networks. In this paper, we propose a novel hyper-generation GAs (HG-GA) concept to approach the fast convergence.
By the HG-GA, a pipelined mechanism can be adopted to speed up the chromosome generating process. Due to the fast convergent
property of HG-GA, which becomes possible to provide an efficient scheduler for switching variable-length packets in high-speed
and multi-channel optical networks.
Genetic and Evolutionary Computation - GECCO 2003, Genetic and Evolutionary Computation Conference, Chicago, IL, USA, July 12-16, 2003. Proceedings, Part I; 01/2003