NS2版本：2.34
涉及NS2代码文件：
ns-2.34/mac/channel.h
ns-2.34/mac/channel.cc
ns-2.34/mac/wireless-phyExt.h
ns-2.34/mac/wireless-phyExt.cc
ns-2.34/mac/mac-802_11Ext.h
ns-2.34/mac/mac-802_11Ext.cc
ns-2.34/mac/mac-802_11.h
ns-2.34/mac/mac-802_11.cc
ns-2.34/common/packet.h
ns-2.34/tcl/lib/ns-default.tcl
ns-2.34/Makefile
准备工作:
1.复制mac-802_11Ext.{h,cc}，wireless-phyExt.{h,cc}命名为mymac-802_11.{h,cc}，mywireless-phy{h,cc}
2.将mymac-802_11.{h,cc}，mywireless-phy{h,cc}的代码置于自定义的命名空间MYMAC里
代码修改:
1.打开mymac-802_11.h找到
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// XXX This header does not have its header access function because it shares
// the same header space with hdr_mac.
struct hdr_mac802_11 {
struct frame_control dh_fc;
u_int16_t dh_duration;
u_char dh_ra[ETHER_ADDR_LEN];
u_char dh_ta[ETHER_ADDR_LEN];
u_char dh_3a[ETHER_ADDR_LEN];
u_int16_t dh_scontrol;
u_char dh_body[0]; // size of 1 for ANSI compatibility
};
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这是NS2中对802.11mac头部的实现，按照NS2文档如果要定义一个新的协议头必须定义static int offset_以及inline static {some mac sturct}* access(const Packet* p)函数，以使NS2能在class Packet中定位到你的头部，这种方法不是很理想，有时候我们只是对已有的头部做一些修改，并不需要重新定义一个头部，按文档的做法会增加不必要的内存 开销，这里我们看上面的注释，翻译过来就是“头部并没有定义自己的头部访问函数，因为它和hdr_mac（定义在mac.h中）使用同样的空间”，这就给 我们提供了另一中添加自定义报头的方法，我们可以在上面的机构中加入我们的数据段，不需要考虑数据对齐的问题，因为上面的头部结构定义在NS2中只是用在 传输头部信息，而真实的数据长度在hdr_cmn.size_中，但是有一点要注意确保 sizeof(hdr_mac802_11)==sizeof(hdr_mac)。那怎么访问自定义头部呢？我们看到packet.h中，找 到#define HDR_MAC802_11(p) ((hdr_mac802_11 *)hdr_mac::access(p))，使用该宏就能定位到自己的头部了。
头部数据已经定义好了，我们得告诉NS2头部数据的真正长度，以便NS2计算传输时间，打开mymac-802_11.cc找到
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void TXC::prepareMPDU(Packet *p) {
hdr_cmn* ch = HDR_CMN(p);
struct hdr_mymac802_11* dh = HDR_MYMAC802_11(p);
ch->size() += mac_->phymib_.getHdrLen11();
dh->dh_fc.fc_protocol_version = MAC_ProtocolVersion;
dh->dh_fc.fc_type = MAC_Type_Data;
dh->dh_fc.fc_subtype = MAC_Subtype_Data;
dh->dh_fc.fc_to_ds = 0;
dh->dh_fc.fc_from_ds = 0;
dh->dh_fc.fc_more_frag = 0;
dh->dh_fc.fc_retry = 0;
dh->dh_fc.fc_pwr_mgt = 0;
dh->dh_fc.fc_more_data = 0;
dh->dh_fc.fc_wep = 0;
dh->dh_fc.fc_order = 0;
dh->dh_scontrol = mac_->sta_seqno_++;
ch->txtime() = mac_->txtime(ch->size(), ch->mod_scheme_);
if ((u_int32_t)ETHER_ADDR(dh->dh_ra) != MAC_BROADCAST) {
dh->dh_duration = mac_->usec(mac_->txtime(mac_->phymib_.getACKlen(),
mac_->phymib_.getBasicModulationScheme())
+ mac_->macmib_.getSIFS());
} else {
dh->dh_duration = 0;
}
}
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看到
ch->size() += mac_->phymib_.getHdrLen11()，getHdrLen11定义如下
getHdrLen11() {
return(HDR_MYMAC_LEN
+ ETHER_FCS_LEN);
}
在mac-802_11Ext中原来实现如下
getHdrLen11() {
return(offsetof(struct hdr_mac802_11, dh_body[0])
+ ETHER_FCS_LEN);
}
使用求偏移得到hdr_mac802_11结构大小，由于我自己添加了3个字节数据在使用偏移会由于对齐问题得到的大小比我实际的大，所以这里不采用偏移
接下来找到
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static class Mac802_11ExtClass : public TclClass {
public:
Mac802_11ExtClass() :
TclClass("Mac/Mac802_11Ext") {
}
TclObject* create(int, const char*const*) {
return (new Mac802_11Ext());
}
} class_mymac802_11;
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将TclClass("Mac/Mac802_11Ext")改为TclClass("Mac/MyMac802_11")，以在tcl中将Mac/MyMac802_11和自定义的mac协议绑定
2.打开mywireless-phy.cc，将#include "wireless-phyExt.h"，#include "mac-802_11Ext.h"改为#include "mywireless-phy.h"，#include "mymac-802_11.h"
找到
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static class WirelessPhyExtClass : public TclClass {
public:
WirelessPhyExtClass() :
TclClass("Phy/WirelessPhyExt") {
}
TclObject* create(int, const char*const*) {
return (new WirelessPhyExt);
}
} class_WirelessPhyExt;
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将TclClass("Phy/WirelessPhyExt")改为TclClass("Phy/MyWirelessPhy")，已以在tcl中将Phy/MyWirelessPhy与自定义的物理层协议绑定
3.打开channel.cc，添加#include "mywireless-phy.h"，找到
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void
WirelessChannel::calcHighestAntennaZ(Phy *tifp)
{
double highestZ = 0;
Phy *n;
// HACK: the dynamic_cast is a workaround only!
for(n = ifhead_.lh_first; n; n = n->nextchnl()) {
if(dynamic_cast<MYMAC::WirelessPhyExt*>(n)) {
if(((MYMAC::WirelessPhyExt *)n)->getAntennaZ() > highestZ)
highestZ = ((MYMAC::WirelessPhyExt *)n)->getAntennaZ();
} else if(dynamic_cast<WirelessPhyExt*>(n)) {
if(((WirelessPhyExt *)n)->getAntennaZ() > highestZ)
highestZ = ((WirelessPhyExt *)n)->getAntennaZ();
} else if (dynamic_cast<WirelessPhy*>(n)) {
if(((WirelessPhy *)n)->getAntennaZ() > highestZ)
highestZ = ((WirelessPhy *)n)->getAntennaZ();
} else highestZ = 0;
}
highestAntennaZ_ = highestZ;
if (dynamic_cast<MYMAC::WirelessPhyExt*>(tifp)) {
MYMAC::WirelessPhyExt *wifp = (MYMAC::WirelessPhyExt *)tifp;
distCST_ = wifp->getDist(wifp->getPowerMonitorThresh(), wifp->getPt(),wifp->getAntennaRxGain(), wifp->getAntennaTxGain(),
highestZ , highestZ, wifp->getL(),
wifp->getLambda());
} else if (dynamic_cast<WirelessPhyExt*>(tifp)) {
WirelessPhyExt *wifp = (WirelessPhyExt *)tifp;
distCST_ = wifp->getDist(wifp->getPowerMonitorThresh(), wifp->getPt(),wifp->getAntennaRxGain(), wifp->getAntennaTxGain(),
highestZ , highestZ, wifp->getL(),
wifp->getLambda());
} else if (dynamic_cast<WirelessPhy*>(tifp)) {
WirelessPhy *wifp = (WirelessPhy *)tifp;
distCST_ = wifp->getDist(wifp->getCSThresh(), wifp->getPt(), 1.0, 1.0,
highestZ , highestZ, wifp->getL(),
wifp->getLambda());
} else distCST_ = DBL_MAX;
}
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这是用来计算天线高度的，上面的有MYMAC名空间的代码都是我添加的
4.打开ns-default.tcl，在里面添加一些默认参数
5.打开Makefile，在OBJ_CC后添加中mymac-802_11.o mywireless-phy.o
最后重新编译自定义的mac协议就添加完成了。
源地址：http://blog.myspace.cn/e/407621022.htm
