27-02-2013, 09:15 AM
RADIO RESOURCE MANAGEMENT & ALLOCATION IN 802.16/WiMAX SYSTEMS
[attachment=51979]
Introduction:
The IEEE 802.16 standard whose industry-led equivalent is also referred to as Worldwide Interoperability for Microwave Access (WiMAX). The Wireless Metropolitan Area Network (WMAN) solution set forth by IEEE in 2001. Later, this standard is revised in 2004 and 2005. Low deployment cost is the main reason for the strong drive towards using WiMAX. The IEEE 802.16 standard describes the Medium Access Protocol and Physical layer of a WMAN. The standard specifies two modes of operation, Point to Multi-Point (PMP) mode, and the optional mesh mode. In PMP mode a Base Station (BS) regulates all the communication in the network, and Subscriber Stations (SS) are only allowed to communicate with the BS. The IEEE 802.16 MAC defines four types of service. Theses services are (a) Unsolicited Grant Service (UGS); (b) Real-Time Polling Service (RTPS); © Non-Real-time Polling Service (NRTPS); and (d) Best Effort Service (BE).
Proposed Research Work
Although the IEEE 802.16 specifications define the signaling messages for the multiple access mechanisms, the radio resource management protocols for sub-carrier allocation, dynamic bandwidth adaptation, connection admission control, and many aspects of network control and management algorithms are unspecified on purpose and left open for innovations by individual equipment vendors as a way to differentiate their products in the marketplace. Protocol engineering for 802.16 broadband wireless systems is an emerging research area where some results have recently been published. However, it holds a greater potential for even comprehensive results addressing relevant issues to support the emerging applications and the development of related concepts and technologies are critical. WiMAX systems are designed to provide high spectral efficiency in order to offer very high data rates to users. The robust physical layer based on the OFDM/OFDMA technique and the use of high-performance coding is partly responsible for the resulting high spectral efficiency.
On the one hand, spectral efficiency is enhanced by WiMAX Radio
Resource Management (RRM) mechanisms. These mechanisms, specified in the IEEE 802.16 standards include admission control, power control, link adaptation and dynamic frequency selection In addition to these radio mechanisms, the WiMAX Forum defines a framework and a functional split of the radio resource management procedures in the WiMAX radio access network (WiMAX architecture is described in. This framework actually further optimize RRM procedures (mainly for admission control and handover) and is especially needed for consistent RRM operations in a multi vendor WiMAX radio network.
As of today, the BS autonomously and independently performs the power control and interference management procedures. However, the RRM framework defined by the WiMAX Forum leaves the door open for further enhancement of the RRM procedures. Possible enhancement could be done by exchanging additional information (e.g. on channel configurations) between RRM entities in order to have a global optimization of radio resources.
The first direction for the future research on RRM algorithms is the MIMO technology. Space-time coding and receive diversity techniques increase network coverage, whereas spatial multiplexing in the DL and collaborative spatial multiplexing in the UL improve spectral efficiency. Adaptive switching between these two MIMO techniques is a promising RRM algorithm. The idea is to use space-time coding for users with bad receiving conditions and to use spatial multiplexing for users with good receiving conditions. The second direction for the future research is a fractional reuse factor. Let us consider three adjacent sectors. We may use the same frequency for the users inside these sectors, and three different frequencies for the users around the edges of these
sectors. In this case, the frequency reuse factor will be between one and three. It is expected that this scheme will have higher spectral efficiency than the fixed frequency reuse factor of one and three. The OFDMA technology and frame structure of the Mobile WiMAX network provide convenient capability for implementing the fractional reuse factor. Another direction is time-frequency scheduling. In the neighboring sectors using the same frequency, different users cause different levels of interference to each other. Consequently, the mutual interference may be reduced by specific allocation of service flows within the time-frequency resource of the frame. Two users that cause the maximum interference to each other may be placed in the areas of non overlapping time-frequency resource. This approach will increase coverage and improve spectral efficiency of the Mobile WiMAX network. Cross-layer optimization of the Mobile WiMAX network for supporting the end-to-end QoS is another interesting direction for research. Under this approach, the Mobile WiMAX network can be optimized for specific services or sets of services. The utility is used to build a bridge between the physical layer and the media access control (MAC) layer and to balance the efficiency and fairness of wireless resource allocation. Cross-layer considerations would be required for designing efficient radio resource management schemes for WiMAX networks. Scheduling control is also another important research area in RRM.
There are many research issues in radio resource management to improve the efficiency and reliability of wireless transmission. The proposed research work investigates in this direction.
SPECTRUM OF RESEARCH GOALS:
• Study of existing algorithms
• Development of efficient algorithms
• Performance analysis and comparison of existing algorithm
[attachment=51979]
Introduction:
The IEEE 802.16 standard whose industry-led equivalent is also referred to as Worldwide Interoperability for Microwave Access (WiMAX). The Wireless Metropolitan Area Network (WMAN) solution set forth by IEEE in 2001. Later, this standard is revised in 2004 and 2005. Low deployment cost is the main reason for the strong drive towards using WiMAX. The IEEE 802.16 standard describes the Medium Access Protocol and Physical layer of a WMAN. The standard specifies two modes of operation, Point to Multi-Point (PMP) mode, and the optional mesh mode. In PMP mode a Base Station (BS) regulates all the communication in the network, and Subscriber Stations (SS) are only allowed to communicate with the BS. The IEEE 802.16 MAC defines four types of service. Theses services are (a) Unsolicited Grant Service (UGS); (b) Real-Time Polling Service (RTPS); © Non-Real-time Polling Service (NRTPS); and (d) Best Effort Service (BE).
Proposed Research Work
Although the IEEE 802.16 specifications define the signaling messages for the multiple access mechanisms, the radio resource management protocols for sub-carrier allocation, dynamic bandwidth adaptation, connection admission control, and many aspects of network control and management algorithms are unspecified on purpose and left open for innovations by individual equipment vendors as a way to differentiate their products in the marketplace. Protocol engineering for 802.16 broadband wireless systems is an emerging research area where some results have recently been published. However, it holds a greater potential for even comprehensive results addressing relevant issues to support the emerging applications and the development of related concepts and technologies are critical. WiMAX systems are designed to provide high spectral efficiency in order to offer very high data rates to users. The robust physical layer based on the OFDM/OFDMA technique and the use of high-performance coding is partly responsible for the resulting high spectral efficiency.
On the one hand, spectral efficiency is enhanced by WiMAX Radio
Resource Management (RRM) mechanisms. These mechanisms, specified in the IEEE 802.16 standards include admission control, power control, link adaptation and dynamic frequency selection In addition to these radio mechanisms, the WiMAX Forum defines a framework and a functional split of the radio resource management procedures in the WiMAX radio access network (WiMAX architecture is described in. This framework actually further optimize RRM procedures (mainly for admission control and handover) and is especially needed for consistent RRM operations in a multi vendor WiMAX radio network.
As of today, the BS autonomously and independently performs the power control and interference management procedures. However, the RRM framework defined by the WiMAX Forum leaves the door open for further enhancement of the RRM procedures. Possible enhancement could be done by exchanging additional information (e.g. on channel configurations) between RRM entities in order to have a global optimization of radio resources.
The first direction for the future research on RRM algorithms is the MIMO technology. Space-time coding and receive diversity techniques increase network coverage, whereas spatial multiplexing in the DL and collaborative spatial multiplexing in the UL improve spectral efficiency. Adaptive switching between these two MIMO techniques is a promising RRM algorithm. The idea is to use space-time coding for users with bad receiving conditions and to use spatial multiplexing for users with good receiving conditions. The second direction for the future research is a fractional reuse factor. Let us consider three adjacent sectors. We may use the same frequency for the users inside these sectors, and three different frequencies for the users around the edges of these
sectors. In this case, the frequency reuse factor will be between one and three. It is expected that this scheme will have higher spectral efficiency than the fixed frequency reuse factor of one and three. The OFDMA technology and frame structure of the Mobile WiMAX network provide convenient capability for implementing the fractional reuse factor. Another direction is time-frequency scheduling. In the neighboring sectors using the same frequency, different users cause different levels of interference to each other. Consequently, the mutual interference may be reduced by specific allocation of service flows within the time-frequency resource of the frame. Two users that cause the maximum interference to each other may be placed in the areas of non overlapping time-frequency resource. This approach will increase coverage and improve spectral efficiency of the Mobile WiMAX network. Cross-layer optimization of the Mobile WiMAX network for supporting the end-to-end QoS is another interesting direction for research. Under this approach, the Mobile WiMAX network can be optimized for specific services or sets of services. The utility is used to build a bridge between the physical layer and the media access control (MAC) layer and to balance the efficiency and fairness of wireless resource allocation. Cross-layer considerations would be required for designing efficient radio resource management schemes for WiMAX networks. Scheduling control is also another important research area in RRM.
There are many research issues in radio resource management to improve the efficiency and reliability of wireless transmission. The proposed research work investigates in this direction.
SPECTRUM OF RESEARCH GOALS:
• Study of existing algorithms
• Development of efficient algorithms
• Performance analysis and comparison of existing algorithm