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IEEE 802.16 based mesh networks: the WOMEN project. D. Tarchi University of Florence tarchi@lart.det.unifi.it. Outline. Wireless Mesh Network: Definition and Characteristics Wireless Mesh Networks: application scenarios QoS scheduling solutions Heterogeneous networks solutions.

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ieee 802 16 based mesh networks the women project

IEEE 802.16 based mesh networks: the WOMEN project

D. Tarchi

University of Florence

tarchi@lart.det.unifi.it

COST 289 - 12th MCM - Firenze, Italy

outline
Outline
  • Wireless Mesh Network: Definition and Characteristics
  • Wireless Mesh Networks: application scenarios
  • QoS scheduling solutions
  • Heterogeneous networks solutions

COST 289 - 12th MCM - Firenze, Italy

women project
WOMEN Project
  • Wireless 8O2.16 Multi-antenna mEsh Networks
  • University of Roma “La Sapienza” + University of Roma “Tor Vergata”
  • University of Napoli “Federico II”
  • University of Firenze
  • University of Catania
  • University of Trento

COST 289 - 12th MCM - Firenze, Italy

research units and wps
Research Units and WPs

WP1 deals with system architecture definition and it is leaded by the

University of Roma "La Sapienza".

WP2 deals with physical layer aspects linked to MIMO technologies and it is leaded by the University of Napoli "Federico II".

WP3 deals with the aspects of Access control and the responsible is the University Firenze

WP4 deals with networking protocols and setup and it is leaded by the University of Catania.

WP5 is responsible for applications, security and trials and is leaded by the University of Trento that has direct access to the WMAN testbed

implemented by CREATE-NET.

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks definition
Wireless Mesh Networks: Definition
  • A Wireless Mesh Network is a multi-hop distributed mesh topology system, with self-configuration and self-organization capabilities, where each node is potentially able to forward Informative Units toward other nearby nodes

I.F. Akyildiz, X. Wang, W. Wang, “Wireless Mesh Networks: a survey” , Computer Networks No.47, pp. 445-487, 2005.

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks characteristics 1 2
Wireless Mesh Networks: Characteristics (1/2)
  • Auto-configuration: all network nodes are designed to self-discover their neighbors and paths without needing of any centralized network entity
  • Auto-organization: nodes can autonomously resolve Out-of-Service events, due to temporary off or congested radio links, by exploiting the Mesh Topology
  • Scalability: the covered area can be extended by simply adding new nodes to the current Mesh Network
  • Mobility: the nodes can move on a limited area and keep the connectivity with (at least) a network node

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks characteristics 2 2
Wireless Mesh Networks: Characteristics (2/2)
  • Mesh Clients: mobile and peripheral nodes able to communicate with other nodes only through radio interfaces. Minimal routing functions are solved by them. Moreover, they are power constrained, typically low cost and developed on already existing Wireless Cards (e.g., 802.11a/b/g Network Interface Cards (NIC) )
  • Mesh Routers: nodes with minimum (or null) mobility, constituting the network backbone, with radio interfaces towards the mesh clients and mesh routers and wired interfaces towards the outside network. They are not power constrained, can process the most of network traffic and results more expensive than the mesh clients.
  • Additional features of the Wireless Mesh Networks: Currently there is no standard, and open questions are related to the security aspects and to proper MAC protocol developments

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks architectures 1 3 infrastructure backbone
Wireless Mesh Networks: architectures (1/3)(Infrastructure/backbone)

IEEE

802.16

  • This architecture is composed by mesh routers which are employed for the wireless backbone and mesh clients are excluded by the mesh topology
  • Connections among the mesh routers are realized with IEEE802.16 technology
  • Mesh routers function also as gateway for Internet access

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks architectures 2 3 client mesh
Wireless Mesh Networks: architectures (2/3)(Client-Mesh)

IEEE 802.11

  • This architecture is composed by self-configured Mesh Clients with routing functions
  • It represents the mesh network operating in ad-hoc mode
  • Currently wireless links are IEEE 802.11 based

COST 289 - 12th MCM - Firenze, Italy

wireless mesh networks architectures 2 3 hybrid mesh
Wireless Mesh Networks: architectures (2/3)(Hybrid-Mesh)

IEEE

802.16

IEEE 802.11

  • This architecture given by combing the two previous ones
  • Mesh Clients can access at the network through mesh routers as well as directly with other mesh clients

COST 289 - 12th MCM - Firenze, Italy

application scenarios 1 2
Broadband home networking

Alternative to IEEE 802.11 and Bluetooth standards

Application Scenarios (1/2)

Community Networking

  • Low cost alternative to link difficult areas to be cabled

COST 289 - 12th MCM - Firenze, Italy

application scenarios 2 2
Application Scenarios (2/2)
  • Metropolitan Wireless Mesh Networks
  • They can be view as a low cost solution of wide band access networks

COST 289 - 12th MCM - Firenze, Italy

research activity
Research Activity
  • WP3 Space division multiple access for QoS guaranteed wide-band connection
    • T3.1 Link adaptation
    • T3.2 Hybrid ARQ Techniques
    • T3.3 Optimized scheduling procedures
  • WP5 Secure applications, development and trials
    • T5.1 Security protocols for multi-hop wireless networks
    • T5.2 Authentication and identity management

COST 289 - 12th MCM - Firenze, Italy

t3 3 optimized scheduling procedures
T3.3 Optimized scheduling procedures
  • IEEE 802.16 Scheduling in OFDM mode
    • Data & VoIP traffic
    • Heterogeneous Scenario with IEEE 802.11 hot-spots

COST 289 - 12th MCM - Firenze, Italy

ieee 802 16 mac
IEEE 802.16 - MAC

The MAC layer can be divided in three sublayers:

  • Convergence Sublayer: management of the IP and ATM interfaces
  • Common Part Sublayer: building of the informative packets, management of the QoS and interfaces with the PHY
  • Privacy Sublayer: management of the cryptography and authentication procedures

Fragmentation

Concatenation

Packing

  • Building and transmissions of PDU
  • PHY support
  • Network inizialization
  • Scheduling services

TDD or FDD (half and/or full duplex)

Framing definition

Timing of DL and UL framing

UGS  guaranteed bandwidth without request

rtPS  request of unicast bandwidth and possibility of a minimum guaranteed bandwidth. No contention

nrtPS  Unicast and contention requests. Minimum guaranteed bandwidth

BES  Contention requests without any guarantee on allocated resources

Define the procedure for the network admission

COST 289 - 12th MCM - Firenze, Italy

quality of service
Quality of Service

The QoS management involves all that transmitting parameters that have influences on the link performance and that, after defining them, have to be maintained

Main parameters:

Throughput

Bandwidth wastage

Delay

Packet-loss

Techniques for QoS control and dynamic resource management (scheduling policy):

Packet Fair Queueing (PFQ): at each queue is assigned a weight that determines the resource allocation. It includes the the techniques based on Round Robin as the Packet Based Round Robin (PBRR)

Earliest Deadline First (EDF): at each queue a priority is assigned basing on the deadline of the first packet to be transmitted

COST 289 - 12th MCM - Firenze, Italy

quality of service application to wimax
Quality of Service – Application to WiMAX

Managed traffic types: UGS, rtPS, nrtPS, BES

BS

Scheduler

Priority:

1 = Max

4 = Min

Strict semi-preemptive priority

UGS

rtPS

nrtPS

BES

1

2

3

4

PFQ Type

Connection IDentifier

PBRR

EDF

Priority Enhanced WFQ

CID

CID

CID

CID

CID

CID

COST 289 - 12th MCM - Firenze, Italy

application environment
Application environment

Joint management of Best-Effort and VoIP traffic in a PMP uplink scenario with a central Base Station and a variable number of user terminals

Voice over Internet Protocol (VoIP): very sensible to transmission delays and queue waiting time

no request

UGS Class  guaranteed bandwidth

PBRR scheduling

Best-Effort: low sensibility to delays and with low constraints

contention requests

BES Class  not guaranteed bandwidth

WFQ scheduling

COST 289 - 12th MCM - Firenze, Italy

framing and contention phases
Framing and contention phases

UL Framing and physical slot structure

Contention

zone

VoIP

Best – Effort

Adaptive threshold

  • Procedures that characterize the system:
  • Contention requests
  • Dynamic bandwidth allocation
  • Packets transmissions

Contention mechanism: random access on one slot that form the contention zone

The slots are chosen with uniform probability

0

1

4

0

2

0

1

3

1

Empty slot

Collisions

Successfull requests

COST 289 - 12th MCM - Firenze, Italy

bandwidth allocation and packets transmission
Bandwidth allocation and packets transmission

The bandwidth allocation and packets transmission occurs in two ways for the two traffic types:

The i-th terminal that can transmit is associated with the weight:

Best Effort

A sufficient number of byte per frame is allocated to each terminal

Weighted scheduling

on the winner terminals

Scheduling PBRR: the

guaranteed bitrate is fixed

VoIP

Each terminal has a bandwidth equal to the allowable bandwidth multiplied by the associated weight

The Base Station transmits the allocated resources to each terminal.

COST 289 - 12th MCM - Firenze, Italy

simulation parameters
TDD transmission structure

Frame duration equal to 1 ms

Channel Bandwidth equal to 25 MHz

5000 Physical Slot per Frame

16QAM Modulation

Transmission rate equal to 80 Mb/s

4 symbols per PS

Trunked Pareto statistic for Best – Effort packet length

ON/OFF VoIP traffic generators with exponential interarrival time having an average value equal to 3 seconds and bitrate equal to 66 kb/s

Simulation Parameters

5000 Byte per UL frame

Fixed UL/DL threshold

Average packet length equal to 480 Byte

10000 Byte per frame

UTRAN

COST 289 - 12th MCM - Firenze, Italy

queue length
Queue Length

The increasing of the contention zone is a good choice until a certain threshold: 25 is the best choice.

COST 289 - 12th MCM - Firenze, Italy

collision percentage
Collision percentage

The performance remains quite similar for a number of slots higher than one half of the BE stations

COST 289 - 12th MCM - Firenze, Italy

successful requests
Successful requests

A small number of contention slot could imply a lower number of requests due to the increasing of collisions

COST 289 - 12th MCM - Firenze, Italy

numerical results for 75 be and 20 be
Numerical results for 75 BE and 20 BE

COST 289 - 12th MCM - Firenze, Italy

voip traffic
VoIP traffic

0.181

64

COST 289 - 12th MCM - Firenze, Italy

heterogeneous network interworking
Heterogeneous network interworking
  • Allows the interoperability with the existing networks
  • Rises the WiMAX coverage in indoor environment
  • Based on standardized network to allow users and operator interoperability
  • Allow a soft-handoff in order to achieve a total coverage

COST 289 - 12th MCM - Firenze, Italy

wi fi vs wimax
Wi-Fi vs. WiMAX

COST 289 - 12th MCM - Firenze, Italy

goals
Goals
  • Simple solution.
  • Interoperability without modifications to the actual standard specifications.
  • QoS management in the interoperability.
  • Simple implementation.

COST 289 - 12th MCM - Firenze, Italy

application scenario
Application scenario

PmP topology

2 transmitting WLAN Wi-Fi

2 receiving WLAN Wi-Fi

WLAN rate equal to 11 Mbit/s

WiMAX link in both uplink and downlink with rate equal to 5.5, 9, 11, 22 Mbit/s.

COST 289 - 12th MCM - Firenze, Italy

mac direct interconnection
MAC direct interconnection

COST 289 - 12th MCM - Firenze, Italy

mac direct interconnection32
MAC direct interconnection
  • The 802.11 frame is directly incapsulated in a MAC PDU 802.16

frame 802.11

frame 802.16

COST 289 - 12th MCM - Firenze, Italy

direct interconnection
Direct interconnection
  • Simple
    • the WiMAX link is a simple tunnel for the WiFi frames
  • Fast
    • low level connection
  • Does not exploit definitely the IEEE 802.16 standard (skip the CS)
  • It implementation requires a specific mapping between IEEE 802.11 and IEEE 802.16 primitives
  • It is not applicable to the IEEE 802.11e.
    • No QoS support

COST 289 - 12th MCM - Firenze, Italy

ethernet bridge interconnection
Ethernet Bridge interconnection

COST 289 - 12th MCM - Firenze, Italy

ethernet bridge interconnection35
Ethernet Bridge interconnection
  • The 802.11e frame is converted in a 802.3ac frame with VLAN tag and then it is sent to the WiMAX link

COST 289 - 12th MCM - Firenze, Italy

ethernet bridge interconnection36
Ethernet Bridge interconnection
  • The SAP in the IEEE 802.16 MAC for the higher layers (LLC or bridge) is the CS_SAP.
  • The SAP in the other IEEE 802 MAC for the higher layers (LLC or bridge) is the MAC_SAP.
  • The other IEEE 802 standards have the same primitives for the MAC_SAP :
    • M_UNITDATA.indication();
    • M_UNITDATA.request();
  • The IEEE 802.16 standard does not define the CS_SAP primitives.

At the exit from the BRIDGE ETHERNET there is a IEEE 802.3ac frame with VLAN tag for the priority support

COST 289 - 12th MCM - Firenze, Italy

simulation parameters wimax link
Simulation parameters – WiMAX link
  • From the above parameters it is possible to derive the MAC PDU size (MAC Header + Payload) in byte:80 : 5000 = (bandwidth) : x
  • where
    • x is the number of PS assigned to the connection.
    • Each PS carries 4 modulation symbols.16 QAM -> 1 symbols with 4 bit => 1 PS is 2 byte

COST 289 - 12th MCM - Firenze, Italy

simulation parameters wifi hot spot self similar model
N sources with ON/OFF period Pareto distributed are aggregated.

200 ON/OFF sources for each generator.

Shape factor (α) for the Pareto distribution of ON/OFF periods equal to 1.4.

Average burst length for each sorce equal to 4000 byte .

Frame dimension uniformly distributed between 34 e 2346 Bytes.

Offered load from the WiFi hot spots between 1.1 Mbit/s to 11 Mbit/s

W. Willinger, M. Taqqu, R. Sherman, and D. Wilson. “Selfsimilarity through high-variability: statistical analysis of Ethernet LAN trafficat the source level,” In Proc. ACM SIGCOMM '95, pp. 100-113, 1995.

Simulation parameters – WiFi hot spot (Self-similar model)

COST 289 - 12th MCM - Firenze, Italy

throughput overhead
Throughput & overhead

COST 289 - 12th MCM - Firenze, Italy

packet delay
Packet delay

COST 289 - 12th MCM - Firenze, Italy

packet delay41
Packet Delay

COST 289 - 12th MCM - Firenze, Italy