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2002-04-23 2
Netlab
Data Networks Lab.
Outline
Protocols with NCR (Neighborhood-aware Contention Resolution)
NAMA, LAMA, PAMA
IEEE 802.11 MAC Overview CSMA/CA IEEE 802.11 for QoS support
Distributed Scheduling
Rate-Adaptive MAC Protocol RBAR(Receiver-Based Autorate)
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Data Networks Lab.
Protocols with NCR
NAMA, LAMA, and PAMA
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Contents
Neighborhood-aware Contention Resolution(NCR) Algorithm
Channel Access Protocols Node Activation Multiple Access (NAMA) Link Activation Multiple Access (LAMA) Pairwise-link Activation Multiple Access (PAMA)
Results
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Neighborhood-aware Contention Resolution
Assumption Every entity knows the set of its contenders. Each contention context (time slot) is
identifiable
NCR Algorithm (in contention context
t)1. (1) Rand( ) is pseudo-random number2. Exit unless (2)3. may access the common channel during
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Channel Access Protocols
Undirected Graph Each node is assigned a unique ID number
Remind the Assumption Nodes already know their neighborhood
Example of Collision Types
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①Node Activation Protocol - NAMA
Based on NCR Node activation Distributed time division multiplexing
Time Division in NAMA
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NAMA Frame Format for Membership
Signal Frame Format in
Membership Section
Data Frame Format in Regular
Section
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NAMA Algorithm
NAMA:
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②Link Active Protocol - LAMA
Based on NCR Time-slotted code division access using
DSSS Link activation (receiver-oriented code
assignment)
Code assignment Orthogonal code pool A receiver is assigned a pseudo-noise
code by the hashing operation
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LAMA Algorithm
The contender set
LAMA:
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LAMA Example
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③Pairwise Link Activation Protocol - PAMA
Based on NCR Time-slotted code division access using DSSS Link activation (transmitter-receiver pair- oriented c
ode assignment)
Contending entities are LINKs, not nodes
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PAMA Algorithm
PAMA:
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Results
Fully Connected - Delay
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Results
Fully Connected - Throughput
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Results
Multihop - Delay
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Results
Multihop - Throughput
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IEEE 802.11 MAC
CSMA/CA & QoS support
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CSMA/CA Example
Source Dest
NAV set NAV setData
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Basic Access Method : CSMA/CA
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IEEE 802.11 QoS support (IEEE 802.11e 에서 표준화 작업 중 )
Using Backoff time Replace by .
Using DIFS
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Distributed Scheduling
Distributed Priority Scheduling
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Contents
Introduction
Distributed Priority Scheduling Proposed Algorithm
Multi-Hop Coordination
Results
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Introduction
Distributed Priority Scheduling Using piggybacked priority tag Each node’s scheduling table will be incomplete →
define probability q
Multi-Hop Coordination Better satisfy end-to-end QoS target across multipl
e nodes
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Distributed Priority Scheduling
Two Scheduler Earliest Deadline First (EDF) → t+d Virtual Clock (VC) → max(t, pk-1) + L/r
802.11 Differentiation backoff timer distribution the defer time (DIFS)
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Algorithm
Priority
Broadcast
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Modified Backoff Policies
Effect of q (available information)
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Multi-Hop Coordination
Definition
Index Assignment Scheme Deadline Targets
Time To Live (TTL) Fixed Per-Node Allocation Uniform Delay Budget (UDB)
Rate Targets
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Simulation Results
Topology
Delay performance
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Rate Adaptive MAC
RBAR(Receiver-Based Autorate)
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Contents
Introduction
Previous Works The Lucent ARF Protocol
The RBAR Protocol Incorporation of RBAR into 802.11
Results
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Introduction
Need for Rate Adaptation
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The Lucent ARF Protocol
Two consecutive ACKs are not received by sender, then drops the rate Timer expires or 10 consecutive ACKs are received, then raises the rat
e
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The Receiver-Based Autorate Protocol
Receiver selects the appropriate rate for the data packet during the RTS/CTS packet exchange (more accurate selection)
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Overview of the RBAR Protocol
S sends a RTS to R with rate r1 and packet-size n.
A hears the RTS and tentatively calculates the reservation duration.
R selects r2 using channel estimation and sends a CTS.
B hears the CTS and calculates the reservation using r2 and n
S puts r2 in the data packet header and transmits at the rate r2.
A hears the data packet and recalculates the reservation.
A S R Br1, nr1, n
r2, n
r2, n r2, n
r2, n
ACK
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RBAR Example
Source Dest
NAV: NAV:DataNAV: 10NAV: 7 NAV: 7
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Incorporation of RBAR into 802.11
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Simulation Results
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Multi-Hop Performance
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Summary
Protocols With NCR New Approach → Using 2-hop neighbor
inform. No need to contend or schedule broadcast
Distributed Priority Scheduling Priority-Based Medium Access Multi-Hop Priority Access
Rate-Adaptive MAC A modified version of 802.11 Improve network throughput
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References
[Protocols with NCR] Lichun Bao and J.J. Garcia-Luna-Aceves, “A New Approach to Channel Access Scheduling for Ad Hoc Networks,” Mobicom 2001.
[IEEE 802.11] Brian P. Crow, Indra Widjaja, Jeong Geun Kim, and Prescott T. Sakai, “IEEE 802.11 wireless local area networks,” IEEE Communication magazine, September 1997.
[802.11 QoS support] Imad Aad and Claude Castelluccia, “Differentiation mechanisms for IEEE 802.11,” Infocom 2001.
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References
[Distributed Scheduling] V. Kanodia, C. Li, A. Sabharwal, B. Sadeghi, and E. Knightly, “Distributed Multi-Hop Scheduling and Medium Access with Delay and Throughput Constraints,” Mobicom 2001.
[Rate-Adaptive MAC] Gavin Holland, Nitin Vaidya, and Paramvir Bahl, “A Rate-Adaptive MAC Protocol for Multi-Hop Wireless Networks,” Mobicom 2001.