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2.2.2.3 802.16 Distributed Uplink
OFDMA uplink access may be performed in a distributed fashion. In fact, the stan-
dardized frame structure of OFDMA in IEEE 802.16 [4] has reserved a control channel
(called the ranging subchannel) for two purposes: synchronization between users and
the base station (i.e., ranging), or requests of uplink transmission from users (i.e., the
uplink bandwidth request). The uplink bandwidth request can optionally be performed
through a contention-based (distributed) mechanism [64]. The details of the mechanism
are however left unstandardized, which provide design opportunities for researchers and
developers. We will propose our solution to this problem based on slotted Aloha and
random backo , in Chapter 4.
2.3 Markov Chain Techniques
The purpose of this section is to summarize main results of Markov chain theory to be
used in this work. We concentrate on the discrete-time Markov chain.
Let A(t); t 2 f0; 1; 2; : : :g be a discrete-time random process that takes on nonnegative
integer values, which are called \states." Then, A(t) is called a Markov chain process if
the current value (or state) of A(t) depends only on A(t 1) but not on any previous
history. That is,
Pr[A(t + 1) = jjA(t) = i;A(t 1) = it1; : : : ;A(0) = i0] = Pr[A(t + 1) = jjA(t) = i]
, Pi;j ; (2.1)
22
Object Description
| Title | Resource allocation in OFDM/OFDMA cellular networks: protocol design and performance analysis |
| Author | Chang, Yu-Jung |
| Author email | yujungc@usc.edu; yjrchang@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2008-09-09 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-29 |
| Advisor (committee chair) | Kuo, C.-C. Jay |
| Advisor (committee member) |
Neely, Michael J. Govindan, Ramesh |
| Abstract | Orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) are two promising technologies adopted in the IEEE 802.16 standard to support broadband wireless access as well as multimedia quality-of-service (QoS). In this dissertation, we discuss several important topics regarding OFDM/OFDMA: cross-layer performance analysis of OFDM and OFDMA downlinks in terms of several QoS metrics; the medium access control (MAC) protocol design for the OFDMA uplink; and the inter-cell interference (ICI) management in multi-cell OFDMA networks through a systematic approach.; First, performance analysis of OFDM-TDMA and OFDMA networks is performed in terms of cross-layer QoS measures which include the bit rate and the bit error rate (BER) in the physical layer, and packet average throughput/delay and packet maximum delay in the link layer. We adopt a cross-layer QoS framework similar to that in IEEE 802.16, where service classification, flow control and opportunistic scheduling with different subcarrier/bit allocation schemes are implemented. Our analysis provides important insights into the performance differences of these two multiaccess systems. In addition, it is shown by analysis and simulation that OFDMA outperforms OFDM-TDMA in QoS metrics of interest. Thus, we conclude that OFDMA has higher potential in supporting multimedia services.; Second, a distributed MAC algorithm for uplink OFDMA networks under the IEEE 802.16 framework is proposed and analyzed. We present a simple yet efficient algorithm to enhance the system throughput by integrating opportunistic medium access and collision resolution through random subchannel backoff. Consequently, the resulting algorithm is called the opportunistic access with random subchannel backoff (OARSB) scheme. OARSB not only achieves distributed coordination among users but also reduces the amount of information exchange between the base station and users. The throughput and delay performance analysis of OARSB is conducted, and the superior performance of OARSB over an existing scheme is demonstrated by analysis as well as computer simulation. Besides, the proposed OARSB scheme can be easily implemented in 802.16 due to its simplicity.; Lastly, a practical and low-complexity multi-cell OFDMA downlink channel assignment method using a graphic framework is proposed. Our solution consists of two phases: 1) a coarse-scale inter-cell interference (ICI) management scheme and 2) a fine-scale channel-aware resource allocation scheme. In the first phase, the task of managing the performance-limiting ICI in cellular networks is accomplished by a graphic approach, in which no ICI measurement is needed and state-of-the-art ICI management schemes such as ICI coordination (ICIC) and base station cooperation (BSC) can be incorporated easily. In the second phase, channel assignment is accomplished by taking instantaneous channel conditions into account. Heuristic algorithms are proposed to solve both phases of the problem efficiently. Extensive simulation is conducted for various practical scenarios to demonstrate the superior performance of the proposed solution against the conventional OFDMA allocation scheme. Thanks to its practicality and low complexity, the proposed scheme can be used in next generation cellular systems such as the 3GPP Long Term Evolution (LTE) and IEEE 802.16m. |
| Keyword | OFDM; OFDMA; MAC protocol design; performance analysis; resource allocation; interference management; IEEE 802.16; cellular networks |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1704 |
| Contributing entity | University of Southern California |
| Rights | Chang, Yu-Jung |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Chang-2392 |
| Archival file | uscthesesreloadpub_Volume40/etd-Chang-2392.pdf |
Description
| Title | Page 36 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 2.2.2.3 802.16 Distributed Uplink OFDMA uplink access may be performed in a distributed fashion. In fact, the stan- dardized frame structure of OFDMA in IEEE 802.16 [4] has reserved a control channel (called the ranging subchannel) for two purposes: synchronization between users and the base station (i.e., ranging), or requests of uplink transmission from users (i.e., the uplink bandwidth request). The uplink bandwidth request can optionally be performed through a contention-based (distributed) mechanism [64]. The details of the mechanism are however left unstandardized, which provide design opportunities for researchers and developers. We will propose our solution to this problem based on slotted Aloha and random backo , in Chapter 4. 2.3 Markov Chain Techniques The purpose of this section is to summarize main results of Markov chain theory to be used in this work. We concentrate on the discrete-time Markov chain. Let A(t); t 2 f0; 1; 2; : : :g be a discrete-time random process that takes on nonnegative integer values, which are called \states." Then, A(t) is called a Markov chain process if the current value (or state) of A(t) depends only on A(t 1) but not on any previous history. That is, Pr[A(t + 1) = jjA(t) = i;A(t 1) = it1; : : : ;A(0) = i0] = Pr[A(t + 1) = jjA(t) = i] , Pi;j ; (2.1) 22 |
