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

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Task Group 4e definitions Date Submitted: July 2008 Source: Pat Kinney, Kinney Consulting LLC Contact: Pat Kinney, Kinney Consulting LLC Voice: +1 847 960-3715, E-Mail: Re: Abstract: Definition of terms to be used by TG4e Purpose: Amendments to IEEE 802.15.4 MAC Notice: This document has been prepared to assist the IEEE P802.15. It 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 IEEE and may be made publicly available by P802.15. Pat Kinney, Kinney Consulting LLC

  2. GTS: Ben Rolfe • Channel Hopping: Chol Su Kang • TDMA:  Paul Dixon • Superframe Structure: Betty Zhao • Time Sync – Chol Su Kang • Mesh – Chol Su Kang • Reliability – Tatsuji Munaka • QoS – Betty Zhao Definitions • Legend • approved • proposed • no proposal received • CSMA/CCA – Paul Dixon • Phy Support – Henk De Ruitjer • Security enhancements – Paul Dixon • Modeling / Simulation – Pat Kinney • Management / Support - Ben Rolfe • Backward Compatibility • Interoperability • Coexistence Pat Kinney, Kinney Consulting LLC

  3. GTS Enhancements: • Extend the existing GTS mechanism in 802.15.4-2006 and enhance GTS management and maintenance.  • Purpose: To address the need for greater control (bounding) of latency, reduce latency, improve delivery reliability for reduced jitter, enable more efficient use of the channel (better payload bits/raw bit rate ratio);  • Application Need: • Support for latency sensitive content as required in interactive applications; • Ability to improve payload/overhead ratio for time critical content; • Reduce packet loss as seen by the next higher layer;  • Scope:  Modify existing MAC with additions and enhancements while preserving interoperability with legacy devices (MAC to MAC) and compatibility with the legacy next-higher-layer(s).  Definitions Pat Kinney, Kinney Consulting LLC

  4. Channel Hopping: • Channel Hopping is a coordinated channel usage scheme. Channel hopping devices in the wireless sensor network are synchronized and select a channel in each synchronized interval (e.g. timeslot) using specified channel hopping sequence. • Channels used in the hopping sequence are based on the IEEE 802.15.4:2006 channels in the 2.4 GHz band. The IEEE 802.15.4:2006 physical layer (2.4 GHz, DSSS) includes 16 channels, numbered 11 through 26. Channel hopping provides channel diversity and help maintaining robust and reliable communication links. Definitions Pat Kinney, Kinney Consulting LLC

  5. Mesh: • Wireless mesh topology is a multi-path peer-to-peer wireless networking topology that includes multi-hop paths. A wireless mesh topology network consists of full-function devices (FFDs) and optional reduced-function devices (RFDs). Wireless mesh topology extends coverage with multi-hop capability and facilitates reliability by utilizing redundant paths between devices. Definitions Pat Kinney, Kinney Consulting LLC

  6. Superframe: • In the beacon-enabled PAN, a superframe structure can be used optionally. The format of the superframe is defined by the coordinator. A superframe must have a beacon frame transmitting in its first slot and can optionally have an active portion and an inactive portion. The beacons are used to synchronize the attached devices, to identify the PAN, and to describe the structure of the superframes. The active portion is divided into equally sized slots and is composed of several parts. Each part contains whole number of consecutive slots and use one certain method to access channel, such as contention, contention-free and any other appropriate methods. Depending on the accessing method, an accessing mechanism is chose, such as CSMA and TDMA. In the inactive portion, the coordinator may enter a low-power (sleep) mode.  • In the nonbeacon-enabled PAN, a superframe structure is not used. (Reference: Paragraph 5.5.1 and 7.5.1 in Std 802.15.4-2006) Definitions Pat Kinney, Kinney Consulting LLC

  7. Time Division Multiple Access (TDMA): • TDMA is a mechanism for dividing up time and allocating it for use by a connection between two or more devices. Unlike GTS which does this on a fairly coarse scale, TDMA allocations can be defined to be multiples of a much smaller unit of time. Definitions Pat Kinney, Kinney Consulting LLC

  8. Quality of Service (QoS): • QoS is a metric of the network’s capability of providing a target service to certain flow utilizing available network resources in the environment of various services coexisting in a PAN and operating in a shared media. The metric may include such parameters as latency, throughput, and reliability of transmission to a certain flow. To achieve the goal, some methods, such as prioritizing and queuing frames, service classification, resource scheduling and data rate control, can be done. • Scope: • Latency • Latency of accessing channel: from receiving a MAC command to transmitting frame successfully (including retries before transmission)     • Latency of association and re-association • Bandwidth - Bulk transfer: data burst during a few seconds (may increase bandwidth according to the requirement) • Throughput • Reliability      • Packet loss      • Reliable reception of broadcast/multicast frame Definitions Pat Kinney, Kinney Consulting LLC

  9. Carrier Sense Multiple Access (CSMA): • CSMA is the scheme that is essentially one step short of anarchy. Any node may send a message during the Contention Access Period where CSMA rules apply. Under such conditions, the potential for conflict and wasted air time is great. Various schemes are imposed to minimise harmful collision. These include Carrier Sense to ensure that no node attempts to start a transmission while there is another transmission in progress. There are ransom back off schemes to minimise the probability that two nodes will begin their transmissions at exactly the same time. The optimum range for this random back off time is dependent on the number of competing nodes. The efficiency of a system can be enhanced by the use of adaptive schemes which iteratively attempt to estimate the number of competitors and adjust the range of their backoff periods depending on this figure to achieve a more optimal performance and higher efficiency and throughput.  Definitions Pat Kinney, Kinney Consulting LLC

  10. Reliability: In many industrial systems, it is indispensable to provide high reliability to end users. We can define the reliability with five aspects: • Fault detection - When a fault occurs, it first detects the fault. This is called fault localization. • Fault diagnosis - After localizing the fault, it diagnoses the localized parts such as nodes or links in the system. • Fault recovery - Then it executes a recovery procedure according to a pre-defined system service. As a result, it removes the fault from the system and may change it to degenerated mode. • Fault analysis - Even though the system goes back to normal status, the system integrator has a responsibility to explain the causes of system-fault and its proposal for relapse prevention. • Reproduce of the fault - If it can not remove the faults, the system integrator is required to reproduce the faults at another backup system. In general, fault management is handled by applications or network management systems. However, current fault management mechanisms are not sufficient to apply the wireless system to industrial systems. In this TG, fault detection and fault recovery which are related with MAC specification are mainly discussed. Definitions Pat Kinney, Kinney Consulting LLC

  11. Security:  There are two major aspects to Security: • control who may join a network • Admission control requires some enhancement to meet the needs of managed systems in the Smart Grid utility world. • ensure that transmissions may not be understood by eavesdroppers. • Encryption is used to achieve the second of these requirements, existing schemes under evaluation by the communications standards are adequate for this purpose Yet such schemes are probably too complex for many home installations. It is probable that a number of levels of security need to be offered, ranging from: • little or no admission control, • minimizing the window of opportunity by push button admission to fully encrypted authorization. • Fully encrypted admission control will be required for utility based Smart Grid applications, where the scheme will entail each node, as well as having a MAC address, having a private encryption key. The key for any authorized node will be known by the utility admission controller and request for admission will be sent encrypted with that key in order that the admission controller can have confidence the MAC address is not being spoofed. • Discussion: should authentication be added to this definition? this definition will be discussed on reflector before next call Definitions Pat Kinney, Kinney Consulting LLC

  12. PHY support: • Adding support to improve the PHY performance in terms of QoS, coexistence and overall system energy consumption by enhanced control of PHY related parameters using control from the MAC via existing PIBs or additional (new) PIBs when needed. The added support may include provision for Antenna Diversity, CCA, CSMA, Frequency Hopping / AFA (Adaptive Frequency Agility). Definitions Pat Kinney, Kinney Consulting LLC

  13. Manage/Support: • Additions to the MAC to better support network forming, configuring and maintenance, manage device configuration and options; • Purpose: • Support the control of all the nifty new features we are adding as part of 4e; • Support NHL applications for better (automatic) control and maintenance of the node and network; • Application Need: • Reduce latency involved with network forming such as device association and re-association; • Provide better support for upper-layer network management needs, such as mesh forming and maintaining; • Provide better visibility and control of QoS and MAC performance; • Scope:  While preserving interoperability with legacy devices, NMS enhancements include: • Additional MLME service definitions, • New MAC management frames, New and/or enhanced Superframe structure; Mechanisms to control QoS parameters which are being enabled; • Mechanisms used to identification of node capabilities; • Additional MAC functions for assessment of performance monitoring Definitions Pat Kinney, Kinney Consulting LLC

  14. Compatibility: • Background • In 802.15.4-2006 [section 5.1] “backward-compatible” is defined as: “in other words, devices conforming to this standard are capable of joining and functioning in a PAN composed of devices conforming to IEEE Std 802.15.4-2003”. This implies the capability to interoperate, in some mode of operation. It does not mandate networks using new and optional behaviors to allow older devices or those without the optional behavior to join. • Backward compatibility: TG4e devices must be able to interoperate/participate with legacy device networks need to maintain SAP for upper layers • Forward compatibility: ability of a legacy device (pre 4e) to interoperate with TG4e networks. This feature would excessively limit the scope of TG4e so it is not a requirement but could be considered to be a feature Definitions Pat Kinney, Kinney Consulting LLC

  15. Coexistence: the ability of one system to perform a task in a given environment where there are other systems that may or may not be using a similar set of rules Interoperability: • The ability of two systems to perform a given task using a single set of rules, • The ability of two or more systems or elements to exchange information and to use the information that has been exchanged (ATLAS/C/PA/SCC20) Modeling: • creation of a tool that yields an approximation of real life parameter Simulation: • The ability of a computer program to accurately predict the behavior of protocols, etc Definitions Pat Kinney, Kinney Consulting LLC