臺灣博碩士論文加值系統

多波束天線藉由增加空間利用率、避免同頻干擾與減少訊號碰撞，來提升無
線網路的吞吐量。多波束天線的應用類似於空間分割多重接取(SDMA)的概念，
每個波束可以視為一個資料通道。另外，倘若實體層支援多速率傳輸能力，無線
網路則可以增加整體的吞吐量並降低傳輸延遲時間。然而，多速率網路存在著不
規則問題。不規則問題是指低速率節點會影響高速率節點應有的吞吐量。這篇論
文假定每個節點搭載多波束天線，且每個波束具有多速率傳輸能力。在同一時間
內，所有波束只能存在傳送模式或是接收模式，而且兩種模式不能同時共存。我
們提出一個以多轉送為基礎的媒體存取控制協定來改善在此種網路下的低速率
節點。我們的方法利用多個轉送節點來建立多個在送者與收者之間的資料通道，
並利用多出來的資料通道去減少傳輸延遲時間。特別是針對低速率節點，冗長的
傳輸延遲時間被分散在由多個轉送節點建立的資料通道，並使得不規則問題得以
減輕。另外，此篇論文解決了由於此種多速率多波束天線運作方式所產生的ACK
同步問題與無用的轉送節點問題。最後，模擬顯示以多轉送為基礎的媒體存取控
制協定可以提高傳輸吞吐量並降低傳輸延遲時間。

Multiple beam antennas can be used to enhance the throughput of wireless networks by
increasing spatial reuse, avoiding co-channel interference, and reducing collisions. The application
of multiple beam antennas is similar to the concept of Space Division Multiple Access
(SDMA), hence each beam can treat as a data channel. Moreover, wireless networks can increase
the total throughput and decrease transmission latency if the physical layer supports
multirate capability. However, multirate wireless networks may bring the anomaly problem.
The anomaly problem is incurred because lower data rate hosts may influence the original performance
of higher data rate nodes. This thesis supposes that each node fits out multiple beam
antennas with multirate capability, and a node can either transmit or receive multiple data on
multiple beams at the same time but not both. We propose a multiple relay-based medium
access control (MAC) protocol to improve throughput of lower data rate hosts. Our MAC protocol
exploits multiple relay nodes and helps the source and the destination to create more than
one data channel to shorten the transmission latency. Especially for low data rate links, the
long-winded transmission latencies are distributed by multiple relay nodes. and the anomaly
problem can be alleviated. In addition, this thesis solves the ACK synchronization problem to
avoid that source nodes can not receive ACK from destination nodes, and adjusts unnecessary
relay nodes during fragment burst period. Finally, simulations show that multiple relay-based
MAC protocol can achieve higher throughput and lower transmission latency.

1 Introduction 1
2 Related works 5
3 Preliminary 10
3.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 Basic Idea of Multiple Relay-based MAC Protocol . . . . . . . . . . . . . . . . . 11
3.3 Challenges of Designing Multiple Relay-based MAC Protocol . . . . . . . . . . . 13
4 Multiple Relay-Based MAC Protocol 17
4.1 Relay Nodes Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2 Multiple Relay-Based MAC protocol . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1 Allotting Multiple Relay Nodes to Desired Destinations . . . . . . . . . . 24
4.2.2 Frame Exchange of Multiple Relay-Based MAC Protocol . . . . . . . . . 28
4.3 Fragment Burst with Adjusting Unnecessary Relay Nodes . . . . . . . . . . . . . 29
5 Performance Analysis 36
5.1 Mathematic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.2 Simulation results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.2.1 Differences between Multiple Relay-Based MAC Protocol and ESIF . . . . 42
5.2.2 Various Relay Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.2.3 Concurrently Multiple Communications . . . . . . . . . . . . . . . . . . . 45
5.2.4 Random Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.2.5 Fragment Burst with Adjusting Relay Nodes . . . . . . . . . . . . . . . . 48
6 Conclusion 50

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