Designing Paradigm-Shifting
Scheduling Algorithms
in Wireless Multimedia Networks
Cloud2Ground Technologies
Cloud2groundte...
Improving QoS…one algo at a time!




Scheduling algorithms are important components in the
provision of guaranteed qual...
Our Technology Addresses All…


QoS requirements for different service classes:

3
Current State…Bottleneck


A typical wireless scheduler

4
Wireless Network Scheduler Challenges...


Characteristics of wireless links




Subject to time- and location-dependen...
Wireless Network Scheduler Challenges cont....




Information needed to make scheduling decisions
 Number of sessions
...
Wireless Network Scheduler Challenges cont....


To maximize MS battery life




To transmit/receive in contiguous time...
Wireless Network Scheduler Challenges cont....


In CDMA network,






the total interference at an MS must be small ...
Our Paradigm Shifting Approach…


Components
(1) An error-free service model
(2) A lead/lag counter


Whether the sessio...
Our Paradigm Shifting Approach cont….
(4) Separate slot queues and session queues for each
session






When a packet ...
Our Technology Features…












Efficient link utilization:
Delay bound:
Fairness:
Throughput:
Implementati...
Our Scheduler Algorithms…


We Build Work-conserving…




The scheduler is never idle if there is a packet awaiting
tra...
Our Scheduler Algorithms cont…


VS. Non-work-conserving
The scheduler may be idle even if there is a
backlogged packet i...
Our Scheduler Algorithms cont.…


We use Timestamps








Incoming packets are timestamped before being placed
in t...
Our Approach To Scheduling in CDMA
Networks…


Advantages of CDMA over TDMA and FDMA









higher (soft) system ...
We leverage…


Advantages of CDMA




The soft capacity feature of CDMA allows a new
session to be established provided...
Our Unique Scheduling Algorithms have…


Topology transparency:






The scheduler works efficiently regardless of ho...
For More Information…


info@cloud2groundtechnologies.com

18
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C2G Wireless Multimedia Networks Technology

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Backgrounder on our High-Performance Algorithms For Wireless Multimedia Networks.

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C2G Wireless Multimedia Networks Technology

  1. 1. Designing Paradigm-Shifting Scheduling Algorithms in Wireless Multimedia Networks Cloud2Ground Technologies Cloud2groundtechnologies.com 1
  2. 2. Improving QoS…one algo at a time!   Scheduling algorithms are important components in the provision of guaranteed quality of service parameters such as delay, delay jitter, packet loss rate, or throughput. The design of scheduling algorithms for mobile communication networks is especially challenging given highly variable link error rates and capacities, and the changing mobile station connectivity. 2
  3. 3. Our Technology Addresses All…  QoS requirements for different service classes: 3
  4. 4. Current State…Bottleneck  A typical wireless scheduler 4
  5. 5. Wireless Network Scheduler Challenges...  Characteristics of wireless links   Subject to time- and location-dependent signal attenuation, fading, interference, and noise that result in bursy errors and time-varying channel capacities. Wireless channel model   Discrete-time Markov chain with two states: error-free (“good”) or error-prone (“bad”) A packet is successfully received if and only if the link stays in the good state throughout the packet transmission time. 5
  6. 6. Wireless Network Scheduler Challenges cont....   Information needed to make scheduling decisions  Number of sessions  Session reserved rates  Link states  Statuses of session queues Information availability  For the down-link:  The scheduler is located at the base station (BS)  This information is easily obtianed  For the up-link:  Some means must be provided to collect queue status information and to inform mobile stations (MSs) of their transmission times. 6
  7. 7. Wireless Network Scheduler Challenges cont....  To maximize MS battery life   To transmit/receive in contiguous time slots and then go into a sleep mode rather than to rapidly switch among transmit, receive and sleep modes. Handoffs   Following a handoff, any packets for S that are queued at previous cell C1’s BS will be forward to current cell C2’s BS For timestamp-based scheduling   Timestamp update Fairness gap: low timestamp  extra service 7
  8. 8. Wireless Network Scheduler Challenges cont....  In CDMA network,    the total interference at an MS must be small enough to ensure an adequate signal-to-interference ration (SIR) for each session, thereby enabling its target bit error rate (BER) to be met. The scheduler must ensure that the number of simultaneous transmissions in the network is not so high as to result in excessive interference. In multihop networks    No BSs Rapidly changing topology Routing 8
  9. 9. Our Paradigm Shifting Approach…  Components (1) An error-free service model (2) A lead/lag counter  Whether the session is leading, in sync with, or lagging its error-free model and by how much (3) A compensation model for each session  A lagging session is compensated at the expense of leading sessions 9
  10. 10. Our Paradigm Shifting Approach cont…. (4) Separate slot queues and session queues for each session    When a packet arrives, it is timestamped and placed in the packet queue; A slot with the same timestamp value is added to the slot queue. If the HOL (Head of line) packet for a session is dropped due either to excessive delay (delay-sensitive) or an excessive number of retransmissions (error-sensitive), the precedence of the session for accessing the channel is maintained by the slot queue. (5) A means for monitoring and predicting the channel state for every backlogged session. 10
  11. 11. Our Technology Features…           Efficient link utilization: Delay bound: Fairness: Throughput: Implementation complexity: Graceful service degradation: Isolation: Energy consumption: Delay/bandwidth decoupling: Scalability: 11
  12. 12. Our Scheduler Algorithms…  We Build Work-conserving…   The scheduler is never idle if there is a packet awaiting transmission. Generalized Processor Sharing (GPS) Weighed Fair Queueing (WFQ) Virtual Clock (VC) Weighted Round Robin (WRR) Self-Clocked Fair Queueing (SCFQ) Deficit Round Robin (DRR) 12
  13. 13. Our Scheduler Algorithms cont…  VS. Non-work-conserving The scheduler may be idle even if there is a backlogged packet in the system because it may be expecting another higher-priority packet to arrive.  Hierarchical Round-Robin (HRR) Stop-and-Go Queuing (SGQ) Jitter-Earliest-Due-Date (Jitter-EDD)  Higher average packet delays than work-conserving  13
  14. 14. Our Scheduler Algorithms cont.…  We use Timestamps     Incoming packets are timestamped before being placed in their respective session queues. The HOL packets are then sorted in increasing order of their timestamps, and the packet with the lowest timestamp value is selected for transmission. Better QoS guarantees VS. Round-robin   No timestamps Easily implemented but lower QoS 14
  15. 15. Our Approach To Scheduling in CDMA Networks…  Advantages of CDMA over TDMA and FDMA       higher (soft) system capacity soft handoff simple frequency planning inherent frequency diversity against multipath fading Voice activity factor and antenna sectorization are readily exploited using CDMA. Drawback  an accurate power control mechanism is required. 15
  16. 16. We leverage…  Advantages of CDMA   The soft capacity feature of CDMA allows a new session to be established provided that the for all transmitting sessions can be maintained above their target levels a certain percentage of the time. The packets sent from a number of MSs can be successfully received simultaneously at the BS, provided an adequate power control scheme is used. 16
  17. 17. Our Unique Scheduling Algorithms have…  Topology transparency:    The scheduler works efficiently regardless of how frequently and unpredictably the topology changes. Our topology independent algorithm reduces the burden of having to recompute and reassign time slots. Low connectivity information requirement:  Some of our algorithms need global network connectivity information while others require only local (e.g., one- or two-hop) connectivity information. 17
  18. 18. For More Information…  info@cloud2groundtechnologies.com 18
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