Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Multiplexing voice and video packet traffic Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης “Traffic Scheduling of Voice and Video Packet Streams in Wireless ATM Networks” S.Psychis and M.Paterakis “A Dynamic Packet Reservation Multiple Access Scheme For Wireless ATM” Deborah A.Dyson and Zygmunt J.Haas

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Voice Terminals Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης P T =P ST /(P ST +P TS ), P S =1-P T Each VT is equipped with a voice activity detector The speech activity is modelled with a two-state Markov chain

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Video Sources Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης α i =(Μ-i)a,β ι =ib,i =0…M Markovian birth-and-death model videos without abrupt scene changes(e.g. Videoconference) State 0 minimum bit rate,state M maximum bit rate

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος The BS Scheduling Algorithm Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης The MTs transmit requests to the BS on a separate request channel The request channel is large enough so contention is kept minimal The S.A. gives priority to Voice terminals The request of a video source is either satisfied in its entirety within the current channel frame,or it is not satisfied at all (e.g, no partial slot allocations are allowed) MPEG-2 or MPEG-4. Priority is given to Video Sources that have not been satisfied in the past.The priority metric counts the total number of video packets lost due to unavailability of slots (packet loss rate)

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Channel Parameters Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης The channel is error free Voice transitions occur at channel frame boundaries The voice packet delay limit is 24msecs (2 frames) Video source rate changes at the beginning of every 3 channel frames The video sequences are encoded to be played back at a rate of 1/0.036=27,7 video frames per second

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Channel Parameters Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης The Peak,minimum and average video bit rates are P =169.2Kbps L=9.6Kbps and AVG=62.4Kbps respectively These numbers correspond to 400X300 pixels per VF, and peak video source rate of 1.41 bits/pixel,average 0.52bits/pixel and minimum 0.08bits/pixel.

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Performance Evaluation Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Performance Evaluation Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Performance Evaluation Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης Mean inter-hit time The time between consecutive events where the slot requests of a video source are not satisfied within the current channel frame

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Packet Reservation Multiple Access Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης A user who needs to gain access waits for an unused slot and then transmits in that slot with probability p.If a collision occurs the user wait for the next empty slot and transmit again with probability p.This continues until the user transmits successfully or decides to give up.If a voice user is successful the same slot in every subsequent frame is reserved for this user. When a user wants to release a slot, the user leaves the next reserved slot empty This process is done by both the voice sources and the video sources. The video sources has to content for every slot that they want to use.

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος DPRMA:Medium Access Control Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης With only Voice users present,the system reverts back to PRMA The primary defference between the two protocols is the manner in which reservations are made and resources are allocated for VBR sources. In DPRMA there are several Reservation Request bits within the header of each uplink time slot. Each user can transmit at a limited number of different transmission rates c i c i = *C/n i min ilog 2 n C is the data rate of the channel,n is the number of slots in a frame,and I is an integer.For this system i min = -3 When a user has a new burst of information to transmit it must first attempt to obtain a reservation.It sets the appropriate RR bits to indicate its rate request. The BS tries to accommodate as much of the rate requested as possible.If the total request can not be fully accommodated,then a partial allocation is made.

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος DPRMA:Medium Access Control Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης The BS must decide which of the remaining unclaimed slots will be assigned. The BS first identifies which slots are currently unallocated and determines how many such slots exists.Next,the base station examines each of these slots in sequential order to determine if the slot will be assigned to accommodate the request.To do that the BS assigns each empty slot with a probability P a where P a =S n /S c.S n is the number of slots the user still needs and S c is the number of available slot. This process ensures that the user will be assigned exactly the number of slots it requires.Also it tends to spread the allocation of slots randomly throughout the frame. When the rate is decreased the BS considers each these slots one at a time in sequential order for deallocation purposes. Each slot is released with probability P d =S d /S r. S d is the number of slots yet to be released and S r the number of slots yet to be considered for release.

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος DPRMA:Medium Access Control Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος DPRMA:Rate Requests Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Voice Traffic Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης For this study,the number of cells that are lost in this manner must not exceed 1% in order to provide an acceptable QOS level.

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Video Conferencing Traffic Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης P=0.9844(By Polyxronis Koutsakis)

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Values of the basic system parameters Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης Peak rate 220/0.04=5500cells/sec

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Threshold levels for video conferencing sources Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Number of voice user spermitted in the system versus voice transmission probability,P Tv Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Total throughput versus voice transmission probability,P Tv Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης

Πρωτόκολλα για Ασύρματα Δίκτυα και ΑΤΜ. Σιγανός Γεώργιος Slots lost due to collisions and reservation release versus voice transmission probability,P Tv Εργαστήριο Τηλεπικοινωνιών Πολυτεχνείο Κρήτης