Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Large System Configurations] Date Submitted: [Sep 5, 2008 ] Source: [Paul Dixon] Company: [Hisilicon] Address: [1700 Alma Drive, Plano TX75075] Voice:[+1 469 229 5374], E-Mail:[pdixon@huawei.com] Re: [IEEE 802.15.4e group] Abstract:This proposal examines the requirements of large widely distributed systems, considering the problems of repeating, routing, channel access using TDMA type schemes etc. Purpose: [To stimulate discussion on the requirements of large widely distributed systems.] Notice: This document is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of the working group for WPANs and may be made publicly available by WPAN. Paul Dixon, Hisilicon

Abstract This presentation examines many aspects that have been discussed for future systems. When applied to large widely distributed systems, many of these interact with each other making it difficult to examine each in isolation. A complete set of these many issues is presented with the interactions identified. The purpose is to stimulate the discussion that is required to bring the specification to the point that covers all these issues. Paul Dixon, Hisilicon

Outline • To examine large and arbitrarily complex systems • To present strategies for configuration, including repeaters and other logical entities • To identify strategies for channel access, including CSMA, TDMA and FDMA • To identify the security models necessary for this class of system Paul Dixon, Hisilicon

Terms • Start by introducing two new terms, Reference Frame and Reference Period • In current systems, the Reference Frame is analogous to the Superframe and the Reference Period analogous to the Beacon Period • The use of these terms does not exclude a regular Beacon, neither does it require one Paul Dixon, Hisilicon

Properties of Systems • Large system where not all devices are able to hear each other • A managed system where the co-ordinator is preassigned by virtue of its properties, e.g. it has a backhaul connection • It will contain some number of redundant elements to ensure adequate tolerance to hardware failures though it should not be considered to be a fault tolerant system Paul Dixon, Hisilicon

Properties of Systems • Start by considering only systems with Fully Functional Devices – RFDs will be introduced later • These devices constitute the core cell of the system • However, they are widely dispersed so not all of them can hear the co-ordinator Paul Dixon, Hisilicon

System Example All devices can hear the coordinator Paul Dixon, Hisilicon

System Example The outer ring cannot hear the coordinator but can all hear at least one device that can hear the coordinator Paul Dixon, Hisilicon

The system can be expanded arbitrarily as required to meet distribution and functionality • Each device may assume a level based on its distance from the coordinator. • Blue devices can hear the coordinator and are at level 1 • Yellow devices can all hear a device at level 1 and are therefore level 2 devices • The next ring will be level 3 etc Paul Dixon, Hisilicon

Repeaters • Since by the previous definition, only devices at level 1 can hear, and therefore communicate directly with, the coordinator, other devices can communicate with the coordinator only if another device is prepared to serve as a repeater • Therefore the functionality of a repeater as a logical entity must be defined and its obligations specified Paul Dixon, Hisilicon

Repeaters Level 1 Level 2 Paul Dixon, Hisilicon

Network Topology • The system can be arranged into a series of layers • Yet not all devices at a given level can hear all others at that level • If a Beacon is transmitted by the NC, only a limited subset of devices will hear this • A more widespread system of synchronisation is required Paul Dixon, Hisilicon

System Synchronisation • The system must retain synchronisation in the absence of the traditional regular Beacon • Inexpensive crystals with sufficient stability to maintain synchronisation over a reasonable time period are available • All devices must issue occasional Beacons with a timestamp taken from a device at the level above • This timestamp allows a system wide Reference Period to be established Paul Dixon, Hisilicon

Beacons • We now move towards a system where Beacons no longer occur at a regular or predictable times • Every device issues a Beacon, which also serves to aid network discovery and identify the Beacon level for a device • Scheduling information will be included in Beacons Paul Dixon, Hisilicon

Channel Access • Within the Reference Period, Reference Frames for Channel Access can be defined • These can include CAP, CFP and inactive periods in any arbitrary combination with multiples of each • A careful layered approach can minimise collisions between hidden nodes in CAP • CFP may employ flexible TDMA or may even use other channels in FDMA Paul Dixon, Hisilicon

Scheduling • In a large system, effective scheduling of traffic is not a trivial task • Since traffic is essentially directed to the NC, the system is busiest in that region • Scheduling becomes a distributed function but must conform to the requirements set out at any higher level Paul Dixon, Hisilicon

Scheduling • TDMA traffic should be considered as connection oriented, e.g. a phone call • The connection is establish at the start and the TDMA stream remains active until the connection is closed • Connections must have a Traffic Specification to ensure the appropriate resources are allocated • Upstream and downstream periods in the Reference Frame assist scheduling Paul Dixon, Hisilicon

Scheduling • TDMA traffic is allocated a defined start time and duration based on the Reference Period • The use of alternate frequencies may be considered to reduce congestion caused by scheduled traffic • This may effectively create a mixed TDMA/FDMA system Paul Dixon, Hisilicon

Routing • Short addressing should be used • Communication is essentially device to coordinator, though peer to peer is supported if required • Devices identify surrounding devices to determine the lowest cost route to the coordinator Paul Dixon, Hisilicon

Routing • Logical addressing of the Network Coordinator should be specified to cater for backup coordinators which would take over in the case of failure • Peer to peer routing should be permitted, though the initial connection to a peer is made through the NC which decides whether to reveal the short address of the peer • Peer to peer route discovery must be supported for this feature Paul Dixon, Hisilicon

Network Identity • The core cell of the network consists entirely of FFDs which are probable owned by the network operator • Other devices, either FFD or RFD, may associate at the discretion of the Network Coordinator • Such devices will associate as a sub cell of the core cell • Association will be through a member of the core cell which will act as a CPE Paul Dixon, Hisilicon

Sub cells • Association with the network will require Authentication to ensure only known and trusted devices may join • Sub cells, although authenticated and associated, will have only limited access and functionality on the core cell Paul Dixon, Hisilicon

Sub cells • The sub cell may be within a home being connected to the core cell through a CPE in the meter • The sub cell may be simple where the CPE also serves as Network Coordinator for that sub cell • The sub cell may also be a more complex standalone network with its own coordinator, but which also wishes to associate with the CPE to permit such interchange of command and information as the core cell offers Paul Dixon, Hisilicon

Sub cells • The ability of a sub cell to operate within the currently defined beacon and non-beacon schemes and that interaction with the local schedules of the core cell must be considered Paul Dixon, Hisilicon

Security • Enhanced security will be the norm in managed systems • Authentication may require individual keys to verify identity • A more flexible strategy of encryption keys may also be required Paul Dixon, Hisilicon

Thank you! Paul Dixon, Hisilicon

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)