1. Analysis and Evaluation of a New MAC Protocol
for Broadband Wireless Access
IEEE Wireless Networks, Communications and Mobile Computing 2005 International Conference
present by Hermes Y.H. Liu
2018/11/22

2. Authors L.F.M. de Moraes P.D. Maciel Jr.
High-Speed Networks Laboratory – RAVEL
Systems Engineering and Computer Science Program
-COPPE/UFRJ (Universidade Federal do Rio de Janeiro)
2018/11/22

3. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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4. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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5. Introduction
IEEE :
- For Broadband Wireless Access (BWA), proposes a wireless high-speed and high performance access system.
- With distinct classes of traffic and QoS
- Do not specify any scheduling algorithm or admission control mechanism to handle QoS
- This article presents a MAC reservation protocol with a traffic scheduling mechanism based on priority rules
- The Access control scheme utilizes TDMA
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6. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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7. IEEE 802.16 Standard A. PHY and MAC Layers - One BS several SSs
- Downlink Channel (DL)
- Uplink Channel (UL)
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8. IEEE 802.16 Standard Channel allocation schemes:
- Frequency Division Duplexing (FDD)
DL and UL use different frequencies
- Time Division Duplexing (TDD)
Both channels share the same frequency and the data in each channel (DL and UL) are transmitted in different time slots
The channel is assumed to be time slotted and composed of fix-length frames, each frame is divided into DL and UL sub-frames
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9. IEEE Standard
- In DL transmission, data are transmitted in broadcast from BS to all the SSs, each SS captures only those packets which are destined to itself
- In UL transmission, SSs request the bandwidth in the Reservation Interval part in the UL sub-frame
- UL-MAP contains Information Element (IE), the time slots which the SS can transmit during the UL sub-frame
only defines the signaling mechanisms for QoS, such as
BW-Request and UL-MAP; is does not define the UL scheduler, the mechanism that determines the IEs in UL-MAP
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10. IEEE 802.16 Standard Figure 1. MAC frame structure in TDD scheme
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11. IEEE 802.16 Standard frame control section
Figure 2. The downlink subframe structure
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12. IEEE 802.16 Standard Figure 3. The uplink subframe structure
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13. IEEE 802.16 Standard B. QoS Architecture
- Unsolicited Grant Service (UGS): need constant bandwidth
- Real-Time Polling Service (rtPS): specific bandwidth and max acceptable delay
- Non- Real- Time Polling Service (nrtPS): intolerant to delay and require a min bandwidth
- Best Effort Service (BE)
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14. IEEE 802.16 Standard Admission Control Uplink Scheduling
Figure 4. QoS architecture of IEEE
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15. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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16. Proposed Protocol Reservation for Bandwidth
Figure 5. MAC frame structure in TDD scheme
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17. Proposed Protocol - SSs use TDMA scheme for Bandwidth Reservation
- Frame lengths are not fixed (different from standard)
- Reservation periods are located at the end of the UL sub-frame (not at the beginning as in )
- BS sends, in the DL sub-frame of the next frame, a UL-MAP with transmission opportunities to reserved SSs.
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18. Proposed Protocol Length of the n-th cycle: (unit: time slot)
Figure 6. Consecutive transmission cycles
Length of the n-th cycle: (unit: time slot)
Transmission cycle:
1. Reservation
2. Downlink
3. UL Transmission
Each reservation period is composed by M slots,
Where M is the no. of stations in the network
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19. Proposed Protocol Version I: GPC (Grants per Connection)
Figure 7. Version I of proposed protocol
Version I: GPC (Grants per Connection)
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20. Proposed Protocol Version II: GPSS (Grants per Subscriber Station)
Figure 8. Version II of proposed protocol
Version II: GPSS (Grants per Subscriber Station)
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21. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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22. Analytic Model A. Version I (GPC) - One BS and M SSs (M>= 1)
- Each SS has infinite buffer-size
- The transmission is error-free and with a rate C bit/s
- The arrival of messages is a Poisson process with
is the arrival rate of class-p messages to station i.
- r.v.s Is the number of packets in m-th
class-p message at i station, average and second moment
be the waiting time (slots) for the n-th class-p message at station i,
that is, from the slot where its transmission across the channel is
initiated
(message per slot)
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23. Analytic Model - The steady- state results for by using a
Markov Ratio Limit Theorem
- The average of class- p message at station i
Where:
is the traffic in the terminal i class p
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24. Analytic Model
Making and take the limits
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25. Analytic Model In the same way, through a recursive equation we obtain
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26. Analytic Model B. Version II (GPSS)
- The classes of the messages exchanged for the numbers of the
stations and vice versa in Version I
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27. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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28. Numeric Results Traffic Classes Scenario I Scenario II Class 1 40% 10%
Table 1. Traffic scenarios used
In scenario I, there is a greater prob. for the high priority class
In scenario II, there is a greater prob. for the low priority class
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29. Numeric Results -10 stations (M=10)
Represents the rate of messages from class p
Represents the rate of messages of class p in the station i
for each p=1,2,3,4 and i= 1,…, 10 -
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30. Numeric Results
Figure in Scenario I: Version I (a) and Version II (b)
In Version I, the priorities between classes prevail over the priorities between stations
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31. Numeric Results
Figure in Scenario II: Version I (a) and Version II (b)
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32. Numeric Results
Figure in Scenario I: Version I (a) and Version II (b)
There are three values of traffic intensity (ρ= 0.3; 0.6; 0.9)
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33. Numeric Results
Figure in Scenario II: Version I (a) and Version II (b)
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34. Agenda - Introduction - IEEE 802.16 Standard - Proposed Protocol
- Analytic Model
- Numeric Results
- Conclutions
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35. Conclusions
The proposed protocol can provide service differentiation between distinct traffic types, decreasing the mean waiting-time for the highest priority class
Version I has fairness between stations, where Version II has significant differences between stations
Future work:
improvement of fairness degree in Version II
include an admission control mechanism
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36. The end, thanks for your patience!!
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