The Integration of Heterogeneous Wireless Networks (IEEE /IEEE ) and its QoS Analysis

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1 141 The Integration of Heterogeneous Wireless Networks (IEEE /IEEE ) and its QoS Analysis Wernhuar Tarng 1, Nai-Wei Chen 1, Li-Zhong Deng 1, Kuo-Liang Ou 1, Kun-Rong Hsie 2 and Mingteh Chen 2 1 Graduate Institute of Computer Science, National Hsinchu University of Education, Taiwan 2 Department of Communication Engineering, Chung Hua University, Hsinchu, Taiwan Abstract: Due to the needs of many demanding users in wireless networks, the transmission distance and bandwidth of IEEE has become inadequate to satisfy their requirements. Therefore, the next generation of wireless network IEEE standard has been developed. The latter has a higher bandwidth to cover a wider area of communication with lower costs in deployment and maintenance, and it also supports quality of service (QoS) in implementation. This paper discusses how to integrate the heterogeneous environments of IEEE and IEEE as well as the design of a QoS mapping mechanism in order to meet the requirements of real-time services by using the allocated bandwidth allocated to a subscriber station. A simulation experiment was conducted to evaluate the efficiency of this mechanism. Keywords: Wireless networks, IEEE , IEEE , real-time services, quality of service. 1. Introduction In recent years, the development of broadband wireless access has made a great progress, and many kinds of wireless network protocols have been proposed, e.g., Bluetooth, Wireless Local Area Network (WLAN), Worldwide Interoperability for Microwave Access (WiMAX), 3rd-Generation Mobile Communication, and Long Term Evolution (LTE). According to the transmission distance, wireless network protocols can be categorized from near to far as: (1) Personal Area Network (PAN), like Bluetooth, (2) WLAN, such as IEEE , and (3) Wireless Wide Area Network (WWAN), such as IEEE For most wireless networks, the users always look for communication services at any time and any place. Therefore, the goal of network engineers is to combine the advantages of different wireless networks to satisfy the needs of most users. In July 1997, IEEE proposed the initial standard [1], and set the Media Access Control (MAC) layer and Physical (PHY) layer protocols. The IEEE protocols could be used in the 2.4GHz frequency band, and the data rate was about 1~2 Mbps. In October 1999, IEEE developed the second standard b [2], with the data rate increased to 11 Mbps, while the other standard a [3] operated in the 5.8 GHz frequency band with the data rate increased to 54 Mbps. In June 2003, IEEE developed the standard of g [4], with the same data rate but using the frequency band in 2.4 GHz. Due to the increasing demand for real-time services, the IEEE working group developed the standard of e in November 2005 to support the quality of service (QoS) in wireless networks [5]. The major purpose of IEEE e is to improve the MAC functions and provide QoS in various service levels through classification and management. The functions for IEEE MAC to access the transmission media include: Distributed Coordination Function (DCF) and Point Coordination Function (PCF) [6]. The former is for the access points (AP) to decide the transmission targets and their order, and the latter uses CSMA/CA mechanism to allocate wireless network resources to the application nodes. When using the PCF mode, the AP needs a polling mechanism to schedule services based on their throughput, delay constraints, fairness and other parameters in order to achieve a better transmission quality and efficiency, but this is rarely used in practice. Due to the complexity of polling mechanisms, most IEEE devices are based on the DCF mode without providing QoS services. As a result, the development of IEEE e was aimed at solving the aforementioned problems. In recent years, the IEEE wireless networks have been widely used in our daily environments such as at home, cafes, libraries, schools, etc, but they also have some problems, for example, transmission distance not far enough, unstable transmission quality, and not applicable to real-time mobile users. To solve these problems, the next-generation wireless network standard IEEE was developed to reduce the network deployment and maintenance efforts while providing more scalability. The attractive features are complementary to wired broadband technologies, such as cable modems and ADSL, so the remote areas without cable networks or densely populated cities can use IEEE wireless networks to reduce the deployment time and maintenance cost. Therefore, IEEE and are being adopted as a solution for extending the reach of the last-mile access to the Internet. Current IEEE standards include: IEEE , IEEE a, IEEE c, IEEE (IEEE d), IEEE (IEEE e), and so on [7]. Depending on how to support mobile services, IEEE standards can be divided into fixed and mobile specifications, among which IEEE , IEEE a, and IEEE d belong to fixed wireless network standards [8], while IEEE e belongs to mobile wireless network standards [9]. IEEE governs a centralized wireless network, which consists mainly of a base station (BS) and several subscriber stations (SS). Its physical layer operates in the 10~66 GHz and 2~11 GHz frequency bands to provide different data rates based on the frequencies and modulation methods. In addition, IEEE provides two operation modes, namely, mesh networks and point to multi-point (PMP) networks. The major difference is that the SS can communicate with each other in the mesh networks without the BS, but a direct transmission between two SS is not feasible in the PMP networks. To support the QoS mechanism, IEEE defines four types of service classes, i.e., Unsolicited Grant Service (UGS), real-time Polling Service (rtps), non-real-time Polling Service

2 142 (nrtps) and Best Effort (BE), by giving a different priority to each class of services. To provide sufficient bandwidth for various services, the BS and SS must create a set of QoS parameters, including the highest transmission rate, the lowest retention rate, and inter-transmission delay. These parameters determine how much data can be transmitted in a frame. In recent years, it is an important issue to guarantee the service quality on wireless networks, especially when across different wireless network environments, e.g., a mobile station connecting from IEEE to IEEE It may be the same from users point of view regarding the requirement of service quality, but the mapping of MAC parameters between these two network environments could be different. Therefore, when a user requests some QoS services in IEEE by providing the related parameters, it is required to transform them into the formats recognized by IEEE while considering the difference of their available bandwidth and the ways of obtaining the bandwidth. Since both IEEE and IEEE are rather popular wireless network standards, it is very important and useful to integrate the heterogeneous environments by designing a QoS mapping mechanism to meet the requirements of real-time services. In the researches of IEEE and IEEE wireless networks, some studies considered the bandwidth allocation based on network loading, for example, Gakhar et al. proposed a mapping method for QoS parameters from IEEE to IEEE [10], with IEEE data streams classified into four service levels. Berlemann et al. investigated the coexistence environment of IEEE and IEEE to analyze the effect on transmission rates and the number of available nodes in the integrated wireless network [11]. Based on Gakhar s results, Niyato and Hossain proposed the mapping of QoS parameters for operation in the mesh networks [12], and analyzed the efficiency of adding the Call Admission Control (CAC) mechanism to a multi-bs environment. Ho and Chao explored how the mobile station (MS) performs hand off in the coexistence environment of IEEE and IEEE [13], and analyzed the efficiency after adding the CAC mechanism. Chen et al. proposed a mapping method for the QoS parameters between IEEE e and IEEE , and conducted a simulation experiment to analyze its performance [14]. The objective of this study is to investigate how to integrate the network environments of IEEE and IEEE and design a QoS mapping mechanism to achieve using the minimum bandwidth to satisfy the requirements of most real-time services to maintain the quality of service. A simulation experiment was conducted to analyze the efficiency of the QoS mapping mechanism. The remainder of this paper is organized as following. Section 2 describes the architecture of the integrated wireless network and the proposed QoS mapping mechanism. Section 3 provides the simulation results and data analysis, and Section 4 includes the conclusion and directions for future studies. 2. Research Method The architecture of the integrated wireless network under investigation is shown in Figure 1, which contains the IEEE d BS to communicate with the IEEE e radio gateway (RG), and several IEEE e QoS stations (QSTA) requesting for QoS services. IEEE d deals with the data transmission of UGS, rtps, nrtps and BE services based on various QoS parameters. To provide the real-time services such as video and voice conferences with a large amount of data transmissions, IEEE e MAC also defines a set of QoS parameters corresponding to the data flow parameters defined by IEEE d [10], i.e., Constant Bit Rate (CBR) with real-time traffic (C1), Variable Bit Rate (VBR) with real-time traffic (C2), VBR with precious data (C3), and unspecified type (C4). These four types of data flows are based on the service types and the required QoS parameters, and it can not conflict with the QoS parameters defined by IEEE d. Figure 1. The integrated wireless networks in this study The internal structure of a RG is shown in Figure 2, where the RG also plays the role of an SS in the IEEE d network. To support the functions of a QoS Access Point (QAP), the RG in the IEEE e network also contains QoS parameters for transmitting and receiving data. When the QAP receives a request from the QSTA, the message contains a traffic identifier (TID) to express the QoS service in the application flow. The QAP will forward the message to the Mapping Module (MM) to transform the service flow parameters into the corresponding QoS parameters supported by IEEE d (Table 1). Table 1. QoS parameter mapping between IEEE e and IEEE d IEEE e IEEE d Traffic Class C1 Traffic Class C1 (UGS) Peak Data Rate, Delay Bound, (Data Rate + Delay Bound) Traffic Class C2 Minimum Data Rate, Peak Data Rate, Delay Bound, Burst Size Traffic Class C3 Minimum Data Rate, Peak Data Rate, User Priority, Burst Size Traffic Class C4 Peak Data Rate, User Priority Maximum Sustained Traffic Rate, Maximum Latency, Tolerated Jitter Traffic Class C2 (rtps) Minimum Reserved Traffic Rate, Maximum Sustained Traffic Rate, Maximum Latency & Traffic Burst Traffic Class C3 (nrtps) Minimum Reserved Traffic Rate, Maximum Sustained Traffic Rate, Traffic Priority, Maximum Traffic Burst Traffic Class C4 (BE) Maximum Sustained Traffic Rate, Traffic Priority

3 143 In the IEEE d environment, it is assumed that the BS s available bandwidth is 75 Mbps and there are five SS. Among them, SS1 is used as the RG for the IEEE e domain. The transmission rate and number of requests for each type of services are shown in Table 2, and the allocation results by the BS algorithm are shown in Table 3. Table 2. Number of requests by each class of services Service Data Rate SS1 SS2 SS3 SS4 SS5 UGS 1024 Kbps rtps 1024 Kbps nrtps 512 Kbps BE 256 Kbps Table 3. Bandwidth allocated to each service class (Mbps) Service SS1 SS2 SS3 SS4 SS5 UGS rtps nrtps BE Total Figure 2. The internal structure of a radio gateway There are two ways for the MM to perform QoS parameter mapping: (1) prioritized mapping, which finds out the priority according to IEEE e TID value (0~7) and then maps it to the equivalent IEEE d service class, and (2) parameterized mapping, which finds out the relative flow parameter according to the TID value (8~15), and then maps it to the equivalent IEEE d service class. When the SS receives a response message from a service flow, it forwards this message to the MM, which will link the Service Flow Identifier (SFID) to the TID received from a service. The mapping between the SFID and the service s TID will continue until the data transmission is completed. In order to achieve fairness while complying with the QoS mapping mechanism, a pair of QoS algorithms was developed for the IEEE d s BS and SS in this study. The BS algorithm is mainly used to allocate bandwidth to the services on all SS, while the SS algorithm is used to allocate bandwidth to the real-time services on an SS, including those in the IEEE e domain, and to carry out their task scheduling. 2.1 The BS algorithm The main purposes of the BS s bandwidth allocation algorithm are (1) allocating bandwidth to all SS based on the bandwidth requirements of their real-time services, (2) deciding the transmission rate for each real-time service, (3) resolving the contentions for network resources among all SS to meet the requirements of real-time services by using the allocated bandwidth. The BS algorithm first determines if its bandwidth can meet the requirements of real-time services on all SS. If the BS has not enough bandwidth to do so, the bandwidth will first be allocated to the higher-priority services with smaller amounts of data, and then the BS will decide whether the remaining bandwidth can still satisfy the requirements of some other real-time services. The flow diagram of the BS algorithm together with its parameters is shown in Appendix 1, and its operation is demonstrated by the following example. According to the above bandwidth allocation results, the total bandwidth requested by all SS (67.5 Mbps) is less than the BS s available bandwidth (75 Mbps), so each service is provided with sufficient bandwidth to transmit data. To realize the situation of insufficient bandwidth for allocation, another SS (SS6) is added in Table 4 to test the BS algorithm, and the allocation results are shown in Table 5. Table 4. Number of requests by each class of services Service Trans. Rate SS1 SS2 SS3 SS4 SS5 SS6 UGS 1024Kbps rtps 1024Kbps nrtps 512Kbps BE 256Kbps Table 5. Bandwidth allocated to each service class (Mbps) Service SS1 SS2 SS3 SS4 SS5 SS6 UGS rtps nrtps BE Total After adding SS6, the bandwidth requested by all SS (80.75Mbps) is higher than the BS can provide (75Mbps). Without sufficient bandwidth, the bandwidth allocated to most SS is lower than before. Because the bandwidth will be allocated to the higher-priority services first, the BE services may not obtain enough bandwidth. Another SS (SS7) is added again in Table 6 to test the situation of BS without sufficient bandwidth for allocation to some real-time services (Table 7). Because SS7 needs a total of 39 Mbps for its UGS services, the BS can only assigned 4Mbps of bandwidth to SS1. Table 6. Number of requests by each class of services Service Trans. Rate SS1 SS2 SS3 SS4 SS5 SS6 SS7 UGS 1024Kbps rtps 1024Kbps nrtps 512Kbps BE 256Kbps

4 144 Table 7. Bandwidth allocated to each class of services (Mbps) Service SS1 SS2 SS3 SS4 SS5 SS6 SS7 UGS rtps nrtps BE Total The SS algorithm The objective of the SS scheduling algorithm is to assign bandwidth to various types of services on the SS, including the services in the IEEE e environment, to satisfy their real-time requirements. The SS algorithm determines whether the available bandwidth can meet the requirements of all its services. If there is not enough bandwidth, it will first allocate the bandwidth to higher-priority services with smaller amounts of data, and then decide if the remaining bandwidth can satisfy the needs of other services. The flow diagram of the SS algorithm with its parameters is shown in Appendix 2, and its operation is demonstrated by the following example. In the IEEE e environment, it is assumed that various types of services are mapped with the parameters through the RG. As shown in Table 8, the bandwidth allocated to SS1 by the BS is 6 Mbps and 4 Mbps after adding SS6 and SS7, respectively. In Section 3, this study will analyze the efficiency of the proposed QoS mapping mechanism by a simulation experiment. The results of various classes of real-time services are provided under the situations that SS1 is assigned with adequate bandwidth (10 Mbps), enough bandwidth (6 Mbps), and insufficient bandwidth (4 Mbps). Table 8. The bandwidth allocated to SS1 (Mbps) Situation UGS rtps nrtps BE Total After adding SS After adding SS Simulation Experiment This study used the Network Simulator 2 [15] to analyze the efficiency of the proposed QoS mapping mechanism. The IEEE e model developed by Technical University Berlin Telecommunication Networks Group (TKN) and the IEEE model developed by Chang Gung University (CGU) [16] were used for simulation. The Media Independent Handover (HIM) topology was used to process the message exchanges between IEEE e and d. There are three major parts for the design of simulation experiment, i.e. (1) object-oriented programming in tool command language (TCL) based on the simulation script, network topology, parameters and behavior of simulated objects, (2) integrating of IEEE e and models through HIM topology according to the QoS mapping mechanism to produce the trace file and outputs by NS2, and (3) analyzing the trace log with the parser and drawing the simulation results, including the throughput, delay time, and packet-loss ratio for the 4 classes of services using the software Gnuplot. The parameters for the simulated environment are: (1) the topology size is 2000m 2000m; (2) the bandwidth of IEEE d environment is 75Mbps; (3) the bandwidth of IEEE e environment is 54Mbps; and (4) there are 8 QSTA s with QoS services and the amounts of data for transmission are listed in Table 9. The QoS service parameters for IEEE are shown in Table 10. There are three cases of bandwidth allocation according to their network loading, i.e., 10 Mbps, 6 Mbps, and 4 Mbps. This section will analyze the efficiency of QoS mapping mechanism based on the throughput, delay time, and packet-loss ratio for various classes of services under different load conditions. Table 9. IEEE e services and their data amounts Node Mapping of real-time Services from Data IEEE e to IEEE d Amount QSTA1 Traffic Class C1(Voice) UGS1 10 MBytes QSTA2 Traffic Class C1 (Voice) UGS2 8 Mbytes QSTA3 Traffic Class C1 (Voice) UGS3 5 Mbytes QSTA4 Traffic Class C2 (Video) rtps1 10 MBytes QSTA5 Traffic Class C2 (Video) rtps2 5 Mbytes QSTA6 Traffic Class C3 (Best Effort) nrtps 10 MBytes QSTA7 Traffic Class C4 (Background) BE1 8 Mbytes QSTA8 Traffic Class C4 (Background) BE2 5 Mbytes Table 10. The QoS parameters of IEEE d services Service Class Maximum Data Rate Minimum Data Rate Packet Size Maximum Delay Time UGS 1024 Kbps N/A 256 bytes 25m seconds rtps 1024 Kbps 256 Kbps 256 bytes 50m seconds nrtps 512 Kbps 128 Kbps 256 bytes 100m seconds BE 256 Kbps 64 Kbps 128 bytes 100m seconds 3.1 Throughput Case 1: Total bandwidth allocated to SS1=10Mbps For the case of adequate bandwidth, all the UGS services on SS1 can transmit data at about the maximum speed (Figure 3). For UGS1, its data transmission is completed in 85 seconds and the amount of data transmitted is calculated as 950 Kbps 85 seconds=80750kbits (about 10.1MBytes), consistent with the data amount listed in Table 9. Similarly, the completion times for UGS2 and UGS3 are 70 and 45 seconds, respectively and the data transmitted are also very close to the data amounts (8Mbytes and 5Mbytes) listed in Table 9. Figure 3. The throughput of UGS services (Case 1) The rtps services can use variable rates, from 1024Kbps to 256Kbps, for data transmission depending on the available bandwidth. Deducting the bandwidth used by the UGS services, the remaining bandwidth is enough for the rtps services to transmit data at the maximum speed (Figure 4). Therefore, rtps1 is completed in 85 seconds and the amount of data transmitted is about 10.1MBytes. Similarly, rtps2 is completed in 45 seconds and the amount of data transmitted is about 5.2MBytes. For both services, the data amounts are very close to those listed in Table 9.

5 145 Because BE1 has a larger amount of data (8MBytes), it is completed in 260 seconds, which is out of the display range. BE2 is completed in 170 seconds at the speed of 245Kbps, and the amount of data transmitted is calculated as 245Kbps 170 seconds = 41650Kbits (about 5.2MBytes). The simulation result is very close to the data amount listed in Table 9. Figure 4. The throughput of rtps services (Case 1) Similarly, the nrtps service can use variable rates, from 521Kbps to 128Kbps, for data transmission depending on the available bandwidth. Deducting the bandwidth consumed by the UGS and rtps services, the remaining bandwidth is still enough for the nrtps service to transmit data at about the maximum speed (Figure 5). The nrtps service is completed in 170 seconds and the amount of data transmitted is computed as 475Kbps 170 seconds = Kbits (about 10.1MBytes), showing the simulated result is close to the data amount listed in Table 9. Case 2: Total bandwidth allocated to SS1=6Mbps Although the bandwidth assigned to SS1 is only 6 Mbps, UGS services have the highest priority to transmit data based on the SS algorithm and thus the simulation results are the same as shown in Case 1 (Figure 3). For the rtps services, deducting the bandwidth used by UGS services, the remaining bandwidth is still enough for rtps services to transmit data at the maximum speed, so the simulation results are also the same as shown in Case 1 (Figure 4). For the nrtps of service, although the UGS and rtps services have consumed most bandwidth, the remaining part is still enough for it to transmit data at the maximum speed. Therefore, the simulation result is the same as that in the previous case (Figure 5). Since the BE services are scheduled using the remaining bandwidth, there is no guarantee for the transmission rate. In Case 2, most bandwidth is consumed by the higher-priority services, the rest part is barely enough for BE2 to transmit data at the speed of 245Kbps (BE2 s priority is higher than BE1 due to its smaller file size). Therefore, BE1 only obtains 64Kbps of bandwidth, and it must wait until the completion of UGS1 to release the bandwidth in 45 seconds. After that, BE1 receives enough bandwidth to transmit data at the maximum speed until its completion (Figure 7). Figure 5. The throughput of nrtps service (Case 1) The BE services can also use variable rates, from 256Kbps to 64Kbps, for data transmission depending on the available bandwidth. Deducting the bandwidth consumed by all higher-priority services, the remaining bandwidth is still enough for the BE services to transmit data at near the maximum speed (Figure 6). Figure 6. The throughput of BE services (Case 1) Figure 7. The throughput of BE services (Case 2) Case 3: Total bandwidth allocated to SS1=4Mbps In this case, SS1 is only allocated with 4Mbps of bandwidth, and the purpose is to test if the SS algorithm can meet the requirement of real-time services for the case of insufficient bandwidth. Basically, the bandwidth is enough for the UGS services to transmit data at the maximum speed, so the simulation results are still the same as in Case 1 (Figure 3). Because SS1 is allocated with insufficient bandwidth, the throughput of rtps services is thus affected. Initially, rtps1 and rtps2 can transmit data at the speeds of 250Kbps and 450Kbps, respectively (Figure 8). Then, rtps2 obtains the bandwidth released by UGS3 in 40 seconds to increase its speed to 950Kbps, and rtps1 also increases its speed to 480Kbps at the same time. The data transmitted by rtps2 is calculated as 450Kbps 40seconds + 950Kbps 25seconds = 41750Kbits (about 5.2MBytes), which is very close to the data amount listed in Table 9.

6 146 Figure 8. The throughput of rtps services (Case 3) Kbps after 45 seconds, and the speed is increased further to 250Kbps after 70 seconds. For BE1, the initial speed is 110Kbps after 70 seconds, and then becomes 245Kbps after 90 seconds (Figure 10). 3.2 Delay Time Delay time is an important indicator to analyze the performance of network services, especially for real-time applications. In this study, a simulation experiment is carried out to measure the delay time of service packets when the SS algorithm is used to allocate bandwidth to various services. In Case 1, the assigned bandwidth for SS1 is adequate (10Mbps) for all services to transmit data at their maximum rates, so the delay times are all zero (Figure 11). Since most bandwidth has been used by the UGS and rtps services, the initial transmission rate for the nrtps service is only 110Kbps, which is increased to 240Kbps (from 40 to 70 seconds) and then becomes 480Kbps (after 80 seconds) as more bandwidth is released upon the completion of UGS and rtps services (Figure 9). As the bandwidth is not enough for nrtps to transmit at the maximum speed at the beginning, the SS algorithm will first schedule the nrtps service using a lower data rate and then increase the rate if any of the higher-priority services is completed and releases its bandwidth. Figure 11. The delay time for real-time services (Case 1) Figure 9. The throughput of nrtps service (Case 3) Deducting the bandwidth consumed by the higher-priority services, the bandwidth left for the BE services is less than 50Kbps. In that case, they have to wait until the completion of some higher-priority services to release the bandwidth. Figure 12. The delay time for real-time services (Case 2) Figure 10. The throughput of BE services (Case 3) Because BE2 has a smaller file size, it obtains the released bandwidth first and starts to transmit data at the speed of 110 Figure 13. The delay time for real-time services (Case 3) In Case 2, the total bandwidth allocated to SS1 is 6Mbps, which is just enough to meet the maximum rates of UGS, rtps,

7 147 and nrtps services, so their delay times are all zero (Figure 12). The remaining bandwidth can only be used by one BE service, so the average delay time for the BE services is 30m seconds. In Case 3, the bandwidth allocated to SS1 is 4Mbps, which is only enough to provide the maximum transmission rate for UGS services. As a result, the other services will incur different degrees of delay (Figure 13), especially the BE services have the longest delay time, and it takes 90 seconds for the delay time to reduce to zero. 3.3 Packet-loss Ratio There are many reasons for packet losses during a network transmission. In addition to insufficient network bandwidth, the packet losses may also be due to signal attenuation or interference in wireless networks. The common solution is to transmit data via acknowledgment or error correction in the physical layer. This study analyzed the packet loss due to insufficient bandwidth through a simulation experiment. In Case 1, SS1 is allocated with 10Mbps of bandwidth, which is enough for all services to use the maximum rate to transmit data. Therefore, the packet-loss ratio for all services is 0 (Figure 14). In Case 2, the bandwidth assigned to SS1 is 6Mbps, which is not enough to provide immediate transmissions for the BE services and therefore it results in some packet losses in the first 45 seconds (Figure 15). In Case 3, since only 4Mbps of bandwidth is allocated to SS1, there are packet losses in most services except for the UGS services. Because the rtps services are mainly real-time audio and the maximum delay time is only 50m seconds, the packet-loss ratio is higher than that of the nrtps service. The BE services can not transmit data in the first 40 seconds, so the packet-loss ratio during that time is close to 100% (Figure 16). Figure 14. The packet-loss rate of various services (Case 1) Figure 15. The packet-loss rate of various services (Case 2) Figure 16. The packet-loss rate of various services (Case 3) 4. Conclusion and Future Studies Future wireless networks are often the integration of complex and diverse network environments. This paper describes how to combine the heterogeneous domains of IEEE and IEEE It also proposes a QoS mapping mechanism for the application in the integrated network environment. The goal is to meet the requirements of real-time services by using the minimum bandwidth allocated to a subscriber station. The proposed mechanism can be used at home or in the offices, where the users only require the IEEE environment and lease a RG for connecting to the IEEE s BS. It can save the costs of using physical wires and purchasing any new equipment, and the users can share the wide deployment and popularity of IEEE networks. Traditionally, bandwidth allocation in the IEEE domain is done by the SS which sends requests to the BS. The BS may not be able to allocate bandwidth to some SS due to insufficient bandwidth, and this will cause the delay or packet loss to some important services. Also, network resources may be wasted by excessive message transmissions due to sending requests between the SS and BS. This study proposed a QoS mapping mechanism for the SS to make consistent requests to the BS, and thus reduces the amount of messages delivered. The SS allocates bandwidth to various services according to its scheduling algorithm after obtaining the bandwidth from the BS. Although the lower-priority services may need to transmit data at a lower speed or even wait for some time, but they can receive the released bandwidth from higher-priority services when completed, in stead of waiting for the bandwidth re-allocation by the BS. According to the experimental results, the proposed QoS mapping mechanism can effectively protect the quality of most real-time services while using the released bandwidth from higher-priority services to improve the quality of lower-priority services as well. With the continuous updating of IEEE and IEEE protocols, there are a couple of issues to be explored. (1) The development of wireless networks is becoming faster and more popular, but the frequency band is still limited for data transmission. Thus, a Multi-Input-Multi-Output (MIMO) mechanism can be added to the IEEE and IEEE domains, together with the IEEE n and IEEE m protocols under developed, hoping that the mechanism can meet the increasing demands of vast users. (2) According to the statistics of network portal, the ratio of general usage in personal computers and notebooks is from 6:4 to 7:3. This study explored only the integration of heterogeneous wireless network environments for IEEE and IEEE , but

8 148 the integration of built-in Ethernet cards in many PC s was not considered. Therefore, the access of the integrated network environment requires the purchase of additional network equipment. Thus, the integration of the heterogeneous network environments containing the IEEE 802.3, IEEE , and IEEE domains to achieve the quality of service is necessary in the future. References [1] IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, IEEE Standard , June [2] IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification: High-Speed Physical Layer (PHY) Extension in the 2.4GHz Band, IEEE Standard b, September [3] IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification: High-Speed Physical Layer Extension in the 5GHz Band, IEEE Standard a, September [4] IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification: Further Higher-Speed Physical Layer Extension in the 2.4GHz Band, IEEE Standard g, January [5] IEEE, Status of Project IEEE e, MAC Enhancements for Quality of Service, IEEE Standard, e, July [6] IEEE, Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification: Medium Access Control (MAC) Quality of Service Enhancements, November [7] IEEE, Developing the IEEE Wireless MAN Standard for Wireless Metropolitan Area Networks, [8] IEEE , Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems, October [9] IEEE e-2005, Air Interface for Fixed and Mobile Broadband Wireless Access Systems, February [10] K. Gakhar, A. Gravey & A. Leroy, IROISE: A New QoS Architecture for IEEE and IEEE e Interworking, IEEE International Conference on Broadband Networks, pp , Boston, Massachusetts, USA, October [11] L. Berlemann, C. Hoymann, G. R. Hierz & S. Mangold, Coexistence and Interworking of IEEE and IEEE (e), Proceedings of IEEE 63 rd Vehicular Technology Conference (VCT 2006), pp , May [12] D. Niyato & E. Hossain, Integration of IEEE WLANs with IEEE based Multihop Infrastructure Mesh/Relay Networks: A Game-Theoretic Approach to Radio Resource Management, IEEE Network, Vol. 21, No. 3, pp. 6-14, [13] C. Y. Ho & H. L. Chao, An Implementation of QoS Framework for Heterogeneous Networks, the first International Workshop on System and Software for Wireless SoC, Taipei, Taiwan, December 17, [14] Y. C. Chen, J. H. Hsia, & Y.J. Liao, Advanced Seamless Vertical Handoff Architecture for WiMAX and WiFi Heterogeneous Networks with QoS Guarantees, Computer Communications, Vol. 32, No. 2, pp , [15] NS-2 Simulator, available: [16] NDSL WiMAX module for NS-2 simulator, available:

9 149 Appendix 1: The flow diagram of IEEE d s BS algorithm The parameters in the IEEE d s BS algorithm are defined as the following: BS_:the BS s available bandwidth SS_req_: the bandwidth requested by all services on all SS SS_UGS_: the bandwidth requested by the UGS services on all SS SS_UGS min: the bandwidth requested by the minimum UGS service on all SS SS_rtPS_: the bandwidth requested by the rtps services on all SS SS_rtPS min: the bandwidth requested by the minimum rtps service on all SS SS_nrtPS_: the bandwidth requested by the nrtps services on all SS SS_nrtPS_min: the bandwidth requested by the minimum nrtps service on all SS SS_BE_: the bandwidth requested by the BE services on all SS SS_BE_min: the bandwidth requested by the minimum BE service on all SS SS _ req_ SS _ UGS_ SS _ rtps _ SS _ nrtps_ SS _ BE_ Figure 17. The flow diagram of IEEE d s BS algorithm

10 150 Appendix 2: The flow diagram of IEEE d s SS algorithm The parameters in the IEEE d s SS algorithm are defined as the following: SS_:the bandwidth allocated to an SS UGS_: the bandwidth requested by the UGS services on an SS UGS min: the bandwidth requested by the minimum UGS service on an SS rtps_: the bandwidth requested by the rtps services on an SS rtps min: the bandwidth requested by the minimum rtps service on an SS nrtps_: the bandwidth requested by the nrtps services on an SS nrtps_min: the bandwidth requested by the minimum nrtps service on an SS BE_: the bandwidth requested by the BE services on an SS BE_min: the bandwidth requested by the minimum BE service on an SS UGS_ rtps_ nrtps_ BE _ Figure 18. The flow diagram of IEEE d s SS algorithm