通信网络实验报告
实验一隐终端和暴露终端问题分析
一、实验目的
1、了解无线网络中的载波检测机制；
2、熟悉节点的传输范围、冲突干扰范围、载波检测范围和噪声干扰范围的概念；
3、了解载波检测接入体制中存在的隐终端问题和暴露终端问题；
4、结合仿真实验分析载波检测无线网络中的隐终端问题和暴露终端问题。
二、实验结果
Node: 1, Layer: AppCbrClient, (0) Server address: 2
Node: 1, Layer: AppCbrClient, (0) First packet sent at [s]: 0.000000000
Node: 1, Layer: AppCbrClient, (0) Last packet sent at [s]: 99.990000000
Node: 1, Layer: AppCbrClient, (0) Session status: Not closed
Node: 1, Layer: AppCbrClient, (0) Total number of bytes sent: 5120000
Node: 1, Layer: AppCbrClient, (0) Total number of packets sent: 10000
Node: 1, Layer: AppCbrClient, (0) Throughput (bits per second): 409600
Node: 2, Layer: AppCbrServer, (0) Client address: 1
Node: 2, Layer: AppCbrServer, (0) First packet received at [s]: 0.007438001
Node: 2, Layer: AppCbrServer, (0) Last packet received at [s]: 99.999922073
Node: 2, Layer: AppCbrServer, (0) Average end-to-end delay [s]: 0.739902205
Node: 2, Layer: AppCbrServer, (0) Session status: Not closed
Node: 2, Layer: AppCbrServer, (0) Total number of bytes received: 4975616
Node: 2, Layer: AppCbrServer, (0) Total number of packets received: 9718
Node: 2, Layer: AppCbrServer, (0) Throughput (bits per second): 398078
Node: 3, Layer: AppCbrClient, (0) Server address: 4
Node: 3, Layer: AppCbrClient, (0) First packet sent at [s]: 0.000000000
Node: 3, Layer: AppCbrClient, (0) Last packet sent at [s]: 99.990000000
Node: 3, Layer: AppCbrClient, (0) Session status: Not closed
Node: 3, Layer: AppCbrClient, (0) Total number of bytes sent: 5120000
Node: 3, Layer: AppCbrClient, (0) Total number of packets sent: 10000
Node: 3, Layer: AppCbrClient, (0) Throughput (bits per second): 409600
Node: 4, Layer: AppCbrServer, (0) Client address: 3
Node: 4, Layer: AppCbrServer, (0) First packet received at [s]: 0.003058001
Node: 4, Layer: AppCbrServer, (0) Last packet received at [s]: 99.993058001
Node: 4, Layer: AppCbrServer, (0) Average end-to-end delay [s]: 0.003119031
Node: 4, Layer: AppCbrServer, (0) Session status: Not closed
Node: 4, Layer: AppCbrServer, (0) Total number of bytes received: 5120000
Node: 4, Layer: AppCbrServer, (0) Total number of packets received: 10000
Node: 4, Layer: AppCbrServer, (0) Throughput (bits per second): 409612
三、实验结果分析
通过仿真结果可以看出，节点2无法收到数据。由于节点3是节点1的一个隐终端，节点1无法通过物理载波检测侦听到节点3的发送，且节点3在节点2的传输范围外，节点3无法通过虚拟载波检测延迟发送，所以在节点1传输数据的过程中，节点3完成退避发送时将引起冲突。
四、思考题
1、RTS/CTS能完全解决隐终端问题吗？如果不能，请说明理由。
从理论分析上看，RTS/CTS协议似乎可以完全解决数据链隐藏终端问题，然而在实际网络中并非如此，尤其是在AdHoc 网络中。以节点为中心，存在发送区域和干扰区域。在发送区域内，在没有干扰的情况下，数据包可正常收发；该区域的大小由站点的功率等参数确定，可视为定值。干扰区域是相对于接受节点而言的，在该区域内，节点可以受到来自非相关节点发送的数据的干扰，造成冲突、丢包。RTS/CTS对隐藏终端问题的屏蔽实际上是建立在两区域相等的基础上的，即所有的隐藏终端都位于接受节点发送范围内。此中假设并不成立，干扰区域与收发节点间距有关。
实验二无线局域网DCF协议饱和吞吐量验证
一、实验目的
1、了解IEEE 802.11 DCF 协议的基本原理。
2、理解网络饱和吞吐量的概念。
3、通过仿真对DCF协议饱和吞吐量的二维马尔可夫链模型进行验证。
二、实验结果
Node: 1, Layer: AppCbrClient, (4) Server address: 55
Node: 1, Layer: AppCbrClient, (4) First packet sent at [s]: 0.000000000
Node: 1, Layer: AppCbrClient, (4) Last packet sent at [s]: 99.990000000
Node: 1, Layer: AppCbrClient, (4) Session status: Not closed
Node: 1, Layer: AppCbrClient, (4) Total number of bytes sent: 5120000
Node: 1, Layer: AppCbrClient, (4) Total number of packets sent: 10000
Node: 1, Layer: AppCbrClient, (4) Throughput (bits per second): 409600
Node: 1, Layer: AppCbrClient, (3) Server address: 54
Node: 1, Layer: AppCbrClient, (3) First packet sent at [s]: 0.000000000
Node: 1, Layer: AppCbrClient, (3) Last packet sent at [s]: 99.990000000
Node: 1, Layer: AppCbrClient, (3) Session status: Not closed
Node: 1, Layer: AppCbrClient, (3) Total number of bytes sent: 5120000
Node: 1, Layer: AppCbrClient, (3) Total number of packets sent: 10000
Node: 1, Layer: AppCbrClient, (3) Throughput (bits per second): 409600
Node: 1, Layer: AppCbrClient, (2) Server address: 53
Node: 1, Layer: AppCbrClient, (2) First packet sent at [s]: 0.000000000
Node: 1, Layer: AppCbrClient, (2) Last packet sent at [s]: 99.990000000
