Motorola IEEE 802 15 4 MAC Proposal

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Motorola IEEE 802 15 4 MAC Proposal Powered By Docstoc
					     March 2001                                                                  doc.: IEEE 802.15-01/135r1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [MAC proposal for the Low Rate 802.15.4 Standard]
Date Submitted: [10 March, 2001]
Source: [Ed Callaway]     Company: [Motorola]
Address: [8000 W. Sunrise Blvd., M/S 2141, Plantation, FL 33322]
Voice:[(954) 723-8341], FAX: [(954) 723-3712], E-Mail:[]
Re: [WPAN-802.15.4 Call for Proposals]
Abstract: [This presentation represents Motorola’s proposal for the P802.15.4 MAC standard, emphasizing the
need for a low cost system having excellent battery life.]

Purpose: [Response to WPAN-802.15.4 Call for Proposals]

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.

     Submission                                        Slide 1                              Ed Callaway, Motorola
March 2001                                        doc.: IEEE 802.15-01/135r1

    MAC Proposal for the Low Rate
         802.15.4 Standard

             Ed Callaway, Member of the Technical Staff
                            Motorola Labs
                      Phone: +1-954-723-8341
                       Fax: +1-954-723-3712

Submission                      Slide 2                     Ed Callaway, Motorola
March 2001                                       doc.: IEEE 802.15-01/135r1

                   15.4 is Different!
 • M2M is a major market that needs to be addressed.
 • Requirements differ from those of other WPANs
       – More emphasis on longer battery life and lower cost.
       – Less emphasis on message latency, channel capacity, and
       – Support for larger space and device numbers.
       – Location determination.

 Since the requirements are different, the design should
   be, too!

Submission                       Slide 3                   Ed Callaway, Motorola
March 2001                                                                                                                doc.: IEEE 802.15-01/135r1

                                  Cluster/Mesh Network
• Suitable for a large number of devices
  (Scalable)            Cluster ID = 1
                                                                                                         Cluster ID = 2
               Cluster ID = 0                                                                              1                                          Cluster ID = 4
                                  20                                                                                           6
                                                14                     5                     CH2
               11                                                                                                                                             A
                                                     CH1                                         7                             CH4
                              4        5                                   2

       8                                                  13
                                           6                   1                                                  2

                    DD        0                                                                                                                 CH5
                                           7                                                                               5
  2                                                                3
           1              3                           9                                                               3

                                                                                                               Cluster ID = 3
                                                                                                                                             Cluster ID = 5


• All devices are physically                                                                                                             Cluster ID = 6

identical, except the
“Designated Device” Gateway
Submission                                                                         Slide 4                                                    Ed Callaway, Motorola
  March 2001                                                                    doc.: IEEE 802.15-01/135r1

                 Network Formation
• A “Designated Device” (Gateway) initiates network formation by
  designating Cluster Head 0 (which may be separate from the DD).

                                                                                                        Cluster ID = 1
• Network grows via inquiry/inquiry                      Cluster ID = 0                                                 6

  scan technique, similar to 15.1.          12
                                                                                         14                 5

                                                                       4        5             CH1               2

• Each device is assigned a
                                                 8                                             13                       9
                                                                                    6               1
                                                              DD       0
  network address composed of the           2
                                                     1             3                           9
  Designated Device ID, Cluster ID,                                                 22

  and Device ID (total of 24 bits).                           10

• Designated Device assigns Cluster IDs; cluster heads assign
  device IDs.

  Submission                      Slide 5                                                           Ed Callaway, Motorola
March 2001                                           doc.: IEEE 802.15-01/135r1

 • Each node maintains a “neighbor list” of devices it can hear
   (designating its parent), plus a list of children.

 • Nodes overhear network maintenance messages to identify
   children and the route to them.

 • First step in routing algorithm is to check the neighbor list; if
   destination is on the list, message is sent directly (“wormhole

 • Otherwise, message is sent to the parent; process is repeated until
   a node is reached that has the destination as a child (or on its
   neighbor list).

Submission                        Slide 6                      Ed Callaway, Motorola
March 2001                                       doc.: IEEE 802.15-01/135r1

                  Network Frame
• To lower power consumption, node duty cycle is reduced to 0.1%.
• However, for an asynchronous system, two nodes are unlikely to be
  simultaneously active.
• Further, to achieve the low cost goal, inexpensive time base
  elements (preferably ceramic resonators or, ideally, MEMS devices)
  are desired, which have relatively poor frequency stability.

             1s                           1s

 1 ms                            1 ms                                1 ms

  T                                R                                   T
  x                                x                                   x

Submission                      Slide 7                    Ed Callaway, Motorola
March 2001                                              doc.: IEEE 802.15-01/135r1

                      Aloha Statistics

     – With short (1 ms) transmissions, collisions are unlikely.
     – A liability (poor reference stability) is turned into an asset
     (randomized transmission timing).

Submission                           Slide 8                      Ed Callaway, Motorola
March 2001                                            doc.: IEEE 802.15-01/135r1

        Dedicated Mediation Devices
  • To enable nodes to synchronize, Mediation Devices (MDs),
    which can record and replay messages, are dispersed
    throughout the network.
  • Dedicated MDs receive for a period of time (e.g., 2 s), transmit
    as needed, sleep, then repeat the process
  • MDs, like telephone answering machines, are simple: They
    must record and replay simple control words such as who is
    transmitting, who is desired, timing information, and perhaps
    short messages.

                  Ns                             Ns

      2s                           2s                                        2s

             Tx                             Tx
  Receive              (sleep)   Receive                 (sleep)         Receive

Submission                        Slide 9                          Ed Callaway, Motorola
March 2001                                doc.: IEEE 802.15-01/135r1

                   Aloha, M.D.
 • Periodically each idle device in the network transmits
   an “Any traffic for me?” message.
 • The MD receives these messages, noting the time
   each was sent, and sends appropriate replies when
   the receiver of each node is active.

Submission                 Slide 10                 Ed Callaway, Motorola
     March 2001                                          doc.: IEEE 802.15-01/135r1

1.   Node A sends an “I have traffic for node B”
     message, but B is sleeping. The MD
     intercepts node A’s message, including                         B
     timing information.
2.   When node B checks in with the MD, it           A
     finds out that A has a message, and when A                     MD
     will try to contact again.
3.   Node B now knows A’s schedule, so they
     can now sync on the same time slot and
     start communication.

     Node A
                                 1               3

                  MD             MD Listen

                                     2       2

     Node B
     Submission                          Slide 11                  Ed Callaway, Motorola
March 2001                                 doc.: IEEE 802.15-01/135r1

       Distributed Mediation Devices
 • As a variation of the dedicated mediation device, the
   functionality of the MD can be distributed among all
   nodes in the network.
 • Each node becomes an MD at a random time, then
   returns to normal operation.
 • The frequency with which a node performs the MD
   function depends on several factors, including:
       – Desired battery life
       – Latency requirements
       – Number of nodes in the network

Submission                      Slide 12             Ed Callaway, Motorola
March 2001                                         doc.: IEEE 802.15-01/135r1

                          MAC Size
 • Software implementation of:
       – Rx packet recovery, addressing, system timing
       – Tx packet construction, addressing, system timing
       – Mediation Device function
 • Requires:
       – 32 kB ROM
       – 4 kB RAM
       – 30 k gates CPU core (overkill)
 • 1.8 mm2 in 0.18 um standard CMOS

Submission                        Slide 13                   Ed Callaway, Motorola
  March 2001                                       doc.: IEEE 802.15-01/135r1

• IEEE Standards have an obligation to support industry direction and
  emerging market opportunities.
• Location determination and remote sensing of inventory alone is a
  $25 billion market, growing at 15 to 20% per year … industrial
  control and monitoring is larger still.
• These markets cannot be met with existing star networks, due to
  cost and power concerns.
• In this case, we must produce a standard that supports:
   – applications requiring ultra-low cost & low energy nodes.
   – applications that require large node numbers and scalability.
   – node location determination.
• An innovative solution is needed, and we believe that the Aloha
  MD approach is that solution.

  Submission                      Slide 14                   Ed Callaway, Motorola
March 2001                                                                doc.: IEEE 802.15-01/135r1

                                      Criteria 1             802.15 TG4        Motorola
             1. How many devices are in this low              64000            64000
             rate network?
             2. What are the types of devices in                            sensors and
             that application (e.g. PDA, sensors,                               control
             bar code scanner, etc.)?                                        elements,
                                                                            and storage
             3. Describe how the network is                  automatic           Self-
             initiated.                                                      organizing
                                                                           and activation
             4. How do devices attach and detach         automatic service       Self-
             from the network. Is human                      discovery,     maintaining;
             intervention required?                       optional manual         no
                                                              mode of       intervention
                                                             operation        required.

             5. Describe the traffic flow of the data. bi-directional   bi-directional
                                                       needs to be
             6. Describe the type of data that flows  asynchronous     asynchronous
             in each branch of the network.            data centric;     packetized
                                                     option to support
                                                     communication is
                                                           a plus
Submission                                       Slide 15                            Ed Callaway, Motorola
March 2001                                                               doc.: IEEE 802.15-01/135r1

                                    Criteria 2
             7. How much payload data is typically       0 to 64 bytes    <10 bytes
             in each message?
             8. How often are messages sent?          highly variable;   less than 6
                                                         application       per hour
             9. What is the target latency in the    10ms - 50ms; or         10s
             message transfer?                              >1s
             10. Describe the network topology.       star and mesh; Cluster/mesh
                                                      both desirable
             11. Is there a master node? Where do allowable but not peer-to-peer
             data flows originate and terminate?          required
             Are the devices peer to peer or
             12. Does this network have to               desirable;     yes, through
             interface to a dissimilar network? If      gateway ok         gateway
             so, how should these two networks be
             connected? As a specific example
             how would this be connected to the
             13. If two 802.15.4 low-rate networks       desirable;    yes, through a
             are in range of one another, should        gateway or         gateway
             they interact? If yes, how?                 bridge ok
             14. What is the type of data that would        Data           Primarily
             flow between two low rate networks?       Exchange of        status and
             How often would they communicate?        status, payload     control, as
                                                       and/or control     necessary
Submission                                    Slide 16                             Ed Callaway, Motorola
March 2001                                                                   doc.: IEEE 802.15-01/135r1

                                     Criteria 3
             15. How should these two low rate             describe in      communicate
             networks connect when they are within          proposal          through
             range? Should they configure                                   gateway only
             themselves into one network or only
             communicate between master, for
             16. Do the devices support                      yes, but is     yes, above
             authentication and security?                 supported by           MAC
                                                           layers above
             17. What is the data traffic type?           asynchronous     asynchronous
             (asynchronous)                                 data centric;
                                                        option to support
                                                       communication is
                                                               a plus
             18. What are the battery life                   application     1 - 3 years
             requirements?                               dependent and
                                                          optimized for
                                                         long battery life
                                                           (lower power
                                                         consumption is
                                                          solution is ok)
             19. What is the physical size of the        compact flash /     credit card
             low-rate transceiver?                        credit card or    incl. Antenna
                                                       smaller desirable
Submission                                      Slide 17                                 Ed Callaway, Motorola
March 2001                                                           doc.: IEEE 802.15-01/135r1

                                   Criteria 4
             20. What is the range requirement of   10cm to 10m is      1-30 m
             the application?                       typical; 10m to
                                                       100m with
                                                      tradeoffs is
             21. What is the estimate market size       maximize    many millions
             (units) of the proposed application?     applicability
             22. Would the application benefit form     desirable       <1 to 3
             location awareness? What it the                         meters; on
             required position accuracy and update                  demand up to
             rate?                                                      latency
             Cost / Complexity                       cost is small   a fraction of
                                                       fraction of        15.1
             Technical Feasibility                                        MD
                                                                     in hardware
             Global Utility                                               yes

Submission                                    Slide 18                         Ed Callaway, Motorola