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VoIP AND MOBILITY

VoIP AND MOBILITY. Vishnu Kanipakam. Contents…. Introduction Issues -DSR -AMR -UPSD Conclusion References. VoIP and Mobility…. VoIP…Voice over Internet Protocol.

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VoIP AND MOBILITY

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  1. VoIP AND MOBILITY Vishnu Kanipakam

  2. Contents… • Introduction • Issues -DSR -AMR -UPSD • Conclusion • References VoIP and Mobility

  3. VoIP and Mobility… • VoIP…Voice over Internet Protocol. • Enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN. • Voice over IP traffic might be deployed on any IP network VoIP and Mobility

  4. Contd… • Incoming phone calls can be automatically routed to your VoIP phone, regardless of where you are connected to the network. • Call center agents using VoIP phones can work from anywhere with a sufficiently fast Internet connection. • A user can make and receive phone calls,no matter…where he is present on the globe. • VoIP phones can integrate with other services available over the Internet, including video conversation, message or data file exchange in parallel with the conversation, audio conferencing, managing address books. VoIP and Mobility

  5. ISSUE…1 • How can we reduce interdomain handoff delay and disruption time in voip service (mobile/wireless environments)??? • Can we process message exchange between nodes within the intra domain in the interdomain environment??? VoIP and Mobility

  6. DSR… • Directional Shadow registration is a new approach for seamless VoIP services. • Prevent unnecessary traffic by shadow registration at neighboring cells with a high probability of handoff. • DSR is established security association (SA) between the MN and AAA server (AAAF) in neighboring domain before the actual handoff occurs. VoIP and Mobility

  7. Contd… • DSR includes technique and algorithmfor organizing DSRR (DSR Region) that reduces disruption and unnecessary traffic. • A cell division scheme, DSRR can sense the optimal time for handoff through Regional Cell Division and applied Direction Vector (DV) obtained through Directional Cell Sectoring. VoIP and Mobility

  8. Introduction… • Shadow Registration, which registers prior to handoff, registers at n neighboring cells (denoted by AAAFn). • Shadow Registration uses the Random-walk model, in which the probability for MN to move to neighboring cells is equal. VoIP and Mobility

  9. AIM… • To reduce the interdomain handoff delay and disruption time in VoIP service in Mobile environments. • To minimize the number of neighboring domains to register caused by regional/directional cell filtering. VoIP and Mobility

  10. Mobile computing architecture VoIP and Mobility

  11. Description… • The mobile computing system consists of the fixed/wireless network, MN, BS, and FN (Fixed Node). • The BS with radio interface was linked to the IP network that is a fixed network. • One cell is a logical or geographical area managed by a BS. • The MN can move while connecting to the network. VoIP and Mobility

  12. Contd… • The MN should have radio communication with the BS of the cell where it stays in order to communicate with other MNs or fixed nodes. • The system has to be designed considering the user's mobility. VoIP and Mobility

  13. Proposed solution… VoIP and Mobility

  14. Contd… • A hexagonal cell model which is divided into a geographical unit managed by one BS. • The X-Y coordinate system is showing the allocation identification (ID) of each cell. • A cell is selected at random to starting point(0,0). VoIP and Mobility

  15. Contd… • The cell is a hexagonal with center (that is, ID) (Xc, Yc) and radius (that is,length of a side of triangle) R. • Cells that adjoin for cell (Xc, Yc) have an ID value that is increased or decreased by each 1 on X axis and Y axis. • This ID is used by discernment value of each cell. VoIP and Mobility

  16. Regional Cell Division using Triangle unit… VoIP and Mobility

  17. Contd… • To find HoR (Handoff Region), STR (Shadow Trigger Region), and NRR (None Registration Region) from the Cell Boundary and Handoff Start Boundary. • Threshold becomes shortest distance between the Handoff Start Boundary and Cell Boundary. • Threshold is used to control the accuracy of handoff, and affects the estimate of handoff time and the number of DSRR generated. VoIP and Mobility

  18. Region Organizing by Regional CellDivision… VoIP and Mobility

  19. Directional Cell Sectoring… VoIP and Mobility

  20. The DSRR Decision… VoIP and Mobility

  21. Experiment and Result analysis… • InitialShadow.RegDSR VoIP and Mobility

  22. Conclusion… • A shadow trigger region (STR) that judges registration availability, a None Registration Region (NRR) that filters registration are composed. • Direction Vector: Reflects MN’s moving direction to decide minimal Shadow Registration Region. • DSR adapt to arbitrary cell topologies in which the number of neighboring base stations at different locations may vary. VoIP and Mobility

  23. ISSUE…2 • Can we reduce packet losses (which causes degradation of the synthesized speech) ??? • At the same time, can we take care of bandwidth used by the voice stream??? VoIP and Mobility

  24. FEC… • In VoIP packet losses cause degradation of the synthesized speech. • The distortions may propagate over several consecutive frames since predictors in the codec exploit inter-frame correlations to gain coding efficiency. • To reduce the effects of packet lossForward Error Correction (FEC) that adds redundant information to voice packets can be used. • FEC can reduce the effects of packet loss, it will increase the amount of bandwidth used by the voice stream, which is not desirable. VoIP and Mobility

  25. Packet loss… • The major cause for speech quality degradation in IP-networks is packet loss. • Packet loss usually occurs in routers due to congestion. • Packets may also bedropped in the application, if they are received too late to be useful. • While voice traffic can tolerate some amount of packet loss, a lossrate of a few percent may he harmful to the speech quality. • The amount of packet lossthat can he tolerated depends on the robustness of the used coding algorithm. VoIP and Mobility

  26. Adaptive Multi Rate system for Voice over IP… VoIP and Mobility

  27. Redundant Packets… • Sender based mechanisms for recovering from packet loss can be classified as retransmission-based techniques and Forward Error Correction (FEC) techniques. • For delay sensitive real-time applications, such as telephony, FEC-techniques are dominant because packet losses can he recovered without time-consuming retransmission. • FEC-techniques transmit the speech parameters in two or more consecutive packets. VoIP and Mobility

  28. Examples… VoIP and Mobility

  29. Selective Redundancy… • For low packet loss rates (<2%), packet losses during stationary speech segments are normally concealed well with a conventional Error Concealment Unit (ECU). • Problems with intelligibility occur when onset frames or non-stationary frames are lost. • To maintain the intelligibility, it is possible to enable redundancy only for these sensitive frames, i.e. important frames are transmitted twice while the remaining frames are only transmitted once. VoIP and Mobility

  30. Parameter Interpolation… • Conventional ECUs extrapolate speech codec parameters from the previous frame in case of packet loss. • The parameters in the AMR codec that may be interpolated areLSF parameters, pitch lag and gain factors. • Pitch lags on the other hand are well behaved during steady-state voiced segments. VoIP and Mobility

  31. Partial Redundancy… VoIP and Mobility

  32. Principle… • To transmit a given amount of the most important coded speech bits redundant information as redundant information. • The amount of partial redundancy may depend on the potential gain for the decoded speech as well on the channel quality. VoIP and Mobility

  33. Experiment… VoIP and Mobility

  34. Network Adaptation… • The horizontal bars are proposed working ranges for the different configurations. • Thearrow is a suggested adaptation path that shows which configuration to use depending on the packet loss rate. • The packet loss rate is reported to the encoder via a feedback channel from the decoder VoIP and Mobility

  35. Conclusion… • AMR codec is a suitable choice for voice over IP. • The adaptive capabilities allows for maximizing the quality of service for all network conditions, without increasing the bit-rate significantly. • For packet loss rates below 1%,a high rate mode should be selected to maximize the basic speech coder quality and vice-versa. VoIP and Mobility

  36. ISSUE 3… • Can power consumption be managed in an effective manner for VoIP over wireless LAN applications??? • If yes,what are those mechanismsand how can we implement them??? VoIP and Mobility

  37. An 802.11-based VoIP over WLAN System… VoIP and Mobility

  38. Introduction… • Wireless LAN (WLAN) systems providing broadband wireless access have experienced a spectacular rise in popularity in recent years. • Power consumption of a hand-held device can be managed. • In order to deliver competitive talk time with a digital cordless or cellular device, power conservation during an active voice call becomes necessary. VoIP and Mobility

  39. Contd… • Power-efficient operation via transmit power control and physical layer rate adaptation for systems are some of the mechanisms…but, they are very complex to implement. • Unscheduled Power Save Delivery (UPSD) in combination with the eDCA mechanism is ideally suited for power management. VoIP and Mobility

  40. Unscheduled Power Save Delivery… • UPSD is an option that the STA can choose via proper signaling. • To define an unscheduled service period, which are contiguous periods of time during which a STA is expected to be awake. • If a station establishes a downlink flow and specifies UPSD power management, then the station requests and the AP should deliver buffered frames associated with that flow during an unscheduled service period. VoIP and Mobility

  41. Frame exchange sequence of UPSD VoIP and Mobility

  42. Functioning… • A STA initiates an unscheduled service period by transmitting a trigger frame, where a trigger frame is defined as a data frame associated with an uplink flow having UPSD enabled. • After the AP acknowledges the trigger frame, it should prepare to transmit the frames in its UPSD power save buffer addressed to the triggering STA. • UPSD is well suited to support bi-directional frame exchanges between a voice STA and its AP. VoIP and Mobility

  43. Behavior at the AP Operating UPSD… • All UPSD-capable APs are required to maintain a UPSD status for each admitted downlink flow. • When a STA is inactivemode, all frames destined to that STA should be transmitted immediately, according to the eDCA channel access procedures. • There are two types of power-save buffers in a UPSD-capable AP: the legacy PS buffer and the UPSD buffer. • The legacy buffer is used to buffer downlink frames belonging to flows using legacy power management. • The UPSD buffer isused for UPSD flows. VoIP and Mobility

  44. Contd… • Upon receiving and acknowledging a trigger frame the AP starts an unscheduled service period. • During the unscheduled service period, the AP should attempt to deliver all the buffered UPSD downlink frames addressed to the STA transmitting the trigger. • The AP should also have an aging function to delete pending traffic when it is buffered for an excessive amount of time. VoIP and Mobility

  45. Behavior at a non-AP QSTA Operating UPSD… • A STA initiating an unscheduled service period shall remain awake until the AP indicates that the end of the unscheduled service period has arrived. • A bi-directional flow is considered best suited for using UPSD. VoIP and Mobility

  46. Contd… • In the absence of uplink data flow using UPSD, a STA should create an artificial uplink trigger flow using UPSD if the STA establishes downlink flows using UPSD. • The STA wakes up periodically and sends an empty frame to initiate unscheduled service periods to retrieve buffered downlink frames from the UPSD buffer. VoIP and Mobility

  47. Average Duty Cycle of Voics STAs… Voice only… VoIP and Mobility

  48. Average Duty Cycle of Voice STAs (Voice+Data)… VoIP and Mobility

  49. Conclusion • UPSD is a more efficient power management mechanism than the legacy power save procedure specified in 802.11. • UPSD delivers lower duty cycle and higher system capacity in both the scenarios (Voice only & Voice+Data) • At present, UPSD is one of the best power management mechanism suitable for implementing VoIP services over WLAN. VoIP and Mobility

  50. References… • T. Wilson, et al., “Normative Text for Unscheduled eDCA Power Management,” Submission to 802.11 TGe group, doc 11-03-0698-00-000e, September, 2003. • D. Qiao, S. Choi, A. Soomro, and K. G. Shin, “Energy-efficient PCF operation of IEEE 802.11a Wireless LAN”, IEEE INFOCOM 2002. • IEEE Standard 802.11e, “Media Access Control (MAC)Enhancements for Quality of Service (QoS),” Draft 6.0, December2003 • Ted Tackyoung Kwon, Mario Gerla, and Sajal Das,Subir Das, “Mobility Management for VoIP service:Mobile IP and SIP,” IEEE Wireless Communication,Oct. 2002. VoIP and Mobility

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