1 | /************************************************************************************ |
---|
2 | * Copyright (C) 2008 by Politehnica University of Bucharest and Rutgers University |
---|
3 | * All rights reserved. |
---|
4 | * Refer to LICENSE for terms and conditions of use. |
---|
5 | ***********************************************************************************/ |
---|
6 | //Petroaca - |
---|
7 | package vnsim.network.dsrc; |
---|
8 | |
---|
9 | |
---|
10 | import java.io.ByteArrayInputStream; |
---|
11 | import java.util.Random; |
---|
12 | |
---|
13 | import java.util.ArrayList; |
---|
14 | |
---|
15 | import vnsim.core.events.ReceiveEvent; |
---|
16 | import vnsim.core.events.SendEvent; |
---|
17 | import vnsim.map.object.Globals; |
---|
18 | |
---|
19 | |
---|
20 | |
---|
21 | public class MAC80211 |
---|
22 | { |
---|
23 | private int ChannelState; |
---|
24 | |
---|
25 | private int RXState,TXState; |
---|
26 | |
---|
27 | private int currentTime; |
---|
28 | |
---|
29 | private DsrcFrame currentFrame; |
---|
30 | |
---|
31 | private static final double relError= 1E-12; |
---|
32 | |
---|
33 | //the timer which decides how many simulation times the station will wait until it will reschedule the packet |
---|
34 | private int backoffTimer; |
---|
35 | |
---|
36 | //the sinr threshold for the BPSK code rate |
---|
37 | private double SINRThreshold=Globals.SINRThresholdBPSK; |
---|
38 | |
---|
39 | private Random randBackoff; |
---|
40 | |
---|
41 | //contention window ; varies according to the transmission success or failure |
---|
42 | private int CWSafety,CWVehicleState,CW; |
---|
43 | |
---|
44 | //the EDCA mechanism |
---|
45 | //the safety Access Category in EDCA |
---|
46 | private ArrayList<SendEvent> ACSafety; |
---|
47 | |
---|
48 | //the vehicle state Access Category in EDCA |
---|
49 | private ArrayList<SendEvent> ACVehicleState; |
---|
50 | |
---|
51 | private double receptionRate; |
---|
52 | |
---|
53 | private int receivedOk; |
---|
54 | |
---|
55 | public MAC80211(int currentTime) |
---|
56 | { |
---|
57 | this.ChannelState=Globals.CCA_IDLE; |
---|
58 | |
---|
59 | this.RXState=Globals.RX_IDLE; |
---|
60 | this.TXState=Globals.TX_IDLE; |
---|
61 | |
---|
62 | this.currentTime=currentTime; |
---|
63 | this.currentFrame=new DsrcFrame(); |
---|
64 | |
---|
65 | this.randBackoff=new Random(); |
---|
66 | |
---|
67 | this.CWVehicleState=2; |
---|
68 | |
---|
69 | this.CWSafety=1; |
---|
70 | |
---|
71 | this.CW=0; |
---|
72 | |
---|
73 | this.backoffTimer=this.randBackoff.nextInt(this.CWSafety+1); |
---|
74 | |
---|
75 | /* |
---|
76 | this.CWVehicleState=7; |
---|
77 | this.ACSafety=new ArrayList<SendEvent>(); |
---|
78 | this.ACVehicleState=new ArrayList<SendEvent>(); |
---|
79 | */ |
---|
80 | |
---|
81 | this.receptionRate=0; |
---|
82 | this.receivedOk=0; |
---|
83 | } |
---|
84 | |
---|
85 | public int getChannelState() |
---|
86 | { |
---|
87 | return this.ChannelState; |
---|
88 | } |
---|
89 | |
---|
90 | public void setChannelState(int set) |
---|
91 | { |
---|
92 | this.ChannelState=set; |
---|
93 | } |
---|
94 | |
---|
95 | public byte[] recvFromPhysical(ReceiveEvent re,double sinr,int currentTime) |
---|
96 | { |
---|
97 | |
---|
98 | |
---|
99 | //first check SINR to see if frame is corrupted |
---|
100 | if(re.getSender()==null) |
---|
101 | { |
---|
102 | if(sinr<this.SINRThreshold) |
---|
103 | { |
---|
104 | Globals.DSRC_PACKETS_LOST_CORRUPTED++; |
---|
105 | return null; |
---|
106 | } |
---|
107 | } |
---|
108 | |
---|
109 | |
---|
110 | //CRC check and BER |
---|
111 | //should calculate the SINR and BER of the header of the frame in a different modulation than the rest of the frame |
---|
112 | //calculate PER |
---|
113 | double preambleBits=Globals.DSRC_PREAMBLE_LENGTH*8,headerBits=Globals.DSRC_PHYHEADER_LENGHT*8,dataBits=0; |
---|
114 | |
---|
115 | ByteArrayInputStream byteStream = new ByteArrayInputStream(re.getMessage()); |
---|
116 | |
---|
117 | dataBits=byteStream.available()*8; |
---|
118 | |
---|
119 | double per; |
---|
120 | if((per=calculatePER(sinr,preambleBits,headerBits,dataBits))>Globals.DSRC_PER_THRESHOLD) |
---|
121 | { |
---|
122 | //per checked ok |
---|
123 | //return data to application |
---|
124 | this.RXState=Globals.RX_RECV; |
---|
125 | Globals.DSRC_PACKETS_RECEIVED_OK++; |
---|
126 | this.receivedOk++; |
---|
127 | return re.getMessage(); |
---|
128 | } |
---|
129 | //packet dropped due to bad per check |
---|
130 | |
---|
131 | Globals.DSRC_PACKETS_LOST_PER++; |
---|
132 | |
---|
133 | return null; |
---|
134 | } |
---|
135 | |
---|
136 | public byte[] sendToPhysical(byte[] message,int currentTime) |
---|
137 | { |
---|
138 | |
---|
139 | //DsrcFrame frame=new DsrcFrame(); |
---|
140 | |
---|
141 | //check channel state ; employ backoff timer |
---|
142 | if(this.ChannelState==Globals.CCA_BUSY) |
---|
143 | { |
---|
144 | //channel busy ; pause backoff timer |
---|
145 | //this.setBackoffTimer(this.backoffTimer+1); |
---|
146 | |
---|
147 | //the reason for the faliure to send |
---|
148 | if(this.RXState!=Globals.RX_RECV) |
---|
149 | Globals.DSRC_PACKETS_SEND_FALIURE_RX++; |
---|
150 | else |
---|
151 | Globals.DSRC_PACKETS_SEND_FALIURE_NOISE++; |
---|
152 | |
---|
153 | if(this.TXState!=Globals.TX_RECV) |
---|
154 | this.TXState=Globals.TX_RECV; |
---|
155 | return null; |
---|
156 | } |
---|
157 | |
---|
158 | //EDCA scheduler - sets the CW to the respective value depending on the message priority |
---|
159 | this.EDCAScheduler(message[0]); |
---|
160 | //if(this.TXState==Globals.TX_IDLE) |
---|
161 | //{ |
---|
162 | if(this.backoffTimer==0) |
---|
163 | { |
---|
164 | this.setBackoffTimer(this.randBackoff.nextInt(this.CW+1)); |
---|
165 | this.TXState=Globals.TX_IDLE; |
---|
166 | |
---|
167 | return message; |
---|
168 | |
---|
169 | } |
---|
170 | else |
---|
171 | { |
---|
172 | this.backoffTimer--; |
---|
173 | this.TXState=Globals.TX_RECV; |
---|
174 | return null; |
---|
175 | } |
---|
176 | //} |
---|
177 | //return null; |
---|
178 | } |
---|
179 | |
---|
180 | public void refreshFrameTime(int currentTime) |
---|
181 | { |
---|
182 | if(currentTime-this.currentTime>=Globals.WIRELESS_TRANSMISSION_FRAMES) |
---|
183 | { |
---|
184 | this.RXState=Globals.RX_IDLE; |
---|
185 | this.ChannelState=Globals.CCA_IDLE; |
---|
186 | |
---|
187 | if(currentTime%4==0) |
---|
188 | this.receivedOk=0; |
---|
189 | } |
---|
190 | |
---|
191 | this.currentTime=currentTime; |
---|
192 | |
---|
193 | } |
---|
194 | |
---|
195 | public double calculatePER(double sinr,double preambleNbits,double headerNbits,double dataNbits) |
---|
196 | { |
---|
197 | double psr=1; |
---|
198 | |
---|
199 | psr*=calculateBER(sinr,preambleNbits,Globals.DSRC_DATA_RATE); |
---|
200 | psr*=calculateBER(sinr,headerNbits,Globals.DSRC_PCLP_RATE); |
---|
201 | psr*=calculateBER(sinr,dataNbits,Globals.DSRC_DATA_RATE); |
---|
202 | |
---|
203 | return 1-psr; |
---|
204 | |
---|
205 | } |
---|
206 | |
---|
207 | public double calculateBER(double sinr,double nbits,double dataRate) |
---|
208 | { |
---|
209 | double ber=BPSKBER(sinr,dataRate); |
---|
210 | |
---|
211 | double csr=Math.pow(1-ber, nbits); |
---|
212 | |
---|
213 | return csr; |
---|
214 | } |
---|
215 | |
---|
216 | public double BPSKBER(double sinr,double dataRate) |
---|
217 | { |
---|
218 | double EbNo=sinr * Globals.DSRC_SIGNAL_SPREAD/dataRate; |
---|
219 | |
---|
220 | double z=Math.sqrt(EbNo); |
---|
221 | |
---|
222 | double ber=0.5 * erfc(z); |
---|
223 | |
---|
224 | return ber; |
---|
225 | } |
---|
226 | |
---|
227 | public double erf(double x) |
---|
228 | { |
---|
229 | final double twoSqrtPi=2/Math.sqrt(Math.PI); |
---|
230 | |
---|
231 | if(Math.abs(x) > 2.2) |
---|
232 | return 1.0-erfc(x); |
---|
233 | |
---|
234 | double sum=x,term=x,xsqr=x*x; |
---|
235 | |
---|
236 | int j=1; |
---|
237 | |
---|
238 | do{ |
---|
239 | term*= xsqr/j; |
---|
240 | sum-= term/(2*j+1); |
---|
241 | ++j; |
---|
242 | term*= xsqr/j; |
---|
243 | sum+= term/(2*j+1); |
---|
244 | ++j; |
---|
245 | } while (Math.abs(term/sum) > relError); |
---|
246 | |
---|
247 | return twoSqrtPi*sum; |
---|
248 | |
---|
249 | } |
---|
250 | |
---|
251 | public double erfc(double x) |
---|
252 | { |
---|
253 | final double oneSqrtPi=1/Math.sqrt(Math.PI); |
---|
254 | |
---|
255 | |
---|
256 | if(Math.abs(x) < 2.2) |
---|
257 | return 1.0-erf(x); |
---|
258 | |
---|
259 | if(x<0) |
---|
260 | return 2.0-erfc(-x); |
---|
261 | |
---|
262 | double a=1, b=x; //last two convergent numerators |
---|
263 | double c=x, d=x*x+0.5; //last two convergent denominators |
---|
264 | double q1, q2= b/d; //last two convergents (a/c and b/d) |
---|
265 | double n= 1.0, t; |
---|
266 | |
---|
267 | do { |
---|
268 | t= a*n+b*x; |
---|
269 | a= b; |
---|
270 | b= t; |
---|
271 | t= c*n+d*x; |
---|
272 | c= d; |
---|
273 | d= t; |
---|
274 | n+= 0.5; |
---|
275 | q1= q2; |
---|
276 | q2= b/d; |
---|
277 | } while (Math.abs(q1-q2)/q2 > relError); |
---|
278 | |
---|
279 | return oneSqrtPi*Math.exp(-x*x)*q2; |
---|
280 | } |
---|
281 | |
---|
282 | public void setBackoffTimer(int set) |
---|
283 | { |
---|
284 | this.backoffTimer=(set>this.CWSafety)?this.CWSafety:set; |
---|
285 | |
---|
286 | } |
---|
287 | |
---|
288 | public int getBackoffTimer() |
---|
289 | { |
---|
290 | return this.backoffTimer; |
---|
291 | } |
---|
292 | |
---|
293 | public void recalculateCW(int totalPackets,int currentTime) |
---|
294 | { |
---|
295 | if(currentTime%4==0 && totalPackets!=0) |
---|
296 | { |
---|
297 | double aux=((double)this.receivedOk/totalPackets*100); |
---|
298 | |
---|
299 | if(aux-this.receptionRate>Globals.RECEPTION_RATE_THRESHOLD) |
---|
300 | { |
---|
301 | this.receptionRate=aux; |
---|
302 | this.CWSafety=(this.CWSafety==0)?0:this.CWSafety-1; |
---|
303 | this.CWVehicleState=(this.CWVehicleState==0)?0:this.CWVehicleState-1; |
---|
304 | return; |
---|
305 | } |
---|
306 | |
---|
307 | if(-(aux-this.receptionRate)>Globals.RECEPTION_RATE_THRESHOLD) |
---|
308 | { |
---|
309 | this.receptionRate=aux; |
---|
310 | this.CWSafety++; |
---|
311 | this.CWVehicleState++; |
---|
312 | } |
---|
313 | } |
---|
314 | } |
---|
315 | |
---|
316 | public void EDCAScheduler(int messageType) |
---|
317 | { |
---|
318 | //to be completed with other message types |
---|
319 | switch(messageType) |
---|
320 | { |
---|
321 | case Globals.PROT_EMERGENCY: |
---|
322 | this.CW=this.CWSafety; |
---|
323 | break; |
---|
324 | default: this.CW=this.CWVehicleState; |
---|
325 | break; |
---|
326 | } |
---|
327 | } |
---|
328 | } |
---|