Transcript Motorola IEEE 802.15.4 MAC Proposal

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:[[email protected]]
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
[email protected]
Submission
Slide 2
Ed Callaway, Motorola
March 2001
doc.: IEEE 802.15-01/135r1
15.4 is Different!
Assumptions
• 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
QoS.
– 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
6
Cluster ID = 0
Cluster ID = 4
1
20
14
6
CH2
5
12
11
4
5
8
2
9
13
6
A
CH4
7
CH1
2
1
4
DD
CH5
0
7
5
8
2
3
1
3
9
CH3
3
22
Cluster ID = 3
10
Cluster ID = 5
CH6
• All devices are physically
identical, except the
“Designated Device” Gateway
Submission
Slide 4
Cluster ID = 6
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).
• Network grows via inquiry/inquiry
scan technique, similar to 15.1.
Cluster ID = 1
20
12
14
5
11
4
• Each device is assigned a
network address composed of the
Designated Device ID, Cluster ID,
and Device ID (total of 24 bits).
6
Cluster ID = 0
8
CH1
5
6
DD
7
2
9
13
1
4
0
7
2
1
3
9
3
22
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
Routing
• 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
routing”).
• 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
x
R
x
T
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
Tx
Receive
Submission
2s
Tx
(sleep)
Receive
Slide 9
(sleep)
Receive
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
1.
2.
3.
doc.: IEEE 802.15-01/135r1
Node A sends an “I have traffic for node B”
message, but B is sleeping. The MD
intercepts node A’s message, including
timing information.
When node B checks in with the MD, it
finds out that A has a message, and when A
will try to contact again.
Node B now knows A’s schedule, so they
can now sync on the same time slot and
start communication.
1s
B
A
MD
Node A
1
MD
3
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
Vision
• 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
1. How many devices are in this low
rate network?
2. What are the types of devices in
that application (e.g. PDA, sensors,
bar code scanner, etc.)?
3. Describe how the network is
initiated.
4. How do devices attach and detach
from the network. Is human
intervention required?
802.15 TG4
Motorola
64000
64000
sensors and
control
elements,
data
processing
and storage
(industrial)
automatic
Selforganizing
upon
deployment
and activation
automatic service
Selfdiscovery,
maintaining;
optional manual
no
mode of
intervention
operation
required.
5. Describe the traffic flow of the data.
bi-directional
bi-directional
needs to be
supported
6. Describe the type of data that flows
asynchronous
asynchronous
in each branch of the network.
data centric;
packetized
option to support
synchronous
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
in each message?
8. How often are messages sent?
0 to 64 bytes
<10 bytes
highly variable;
less than 6
application
per hour
dependent
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
master/slave?
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
internet?
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
information
Submission
Slide 16
Ed Callaway, Motorola
March 2001
doc.: IEEE 802.15-01/135r1
Criteria 3
15. How should these two low rate
networks connect when they are within
range? Should they configure
themselves into one network or only
communicate between master, for
example?
16. Do the devices support
authentication and security?
Submission
describe in
proposal
communicate
through
gateway only
yes, but is
yes, above
supported by
MAC
layers above
MAC
17. What is the data traffic type?
asynchronous
asynchronous
(asynchronous)
data centric;
option to support
synchronous
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
better,
asymmetrical
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
Slide 17
Ed Callaway, Motorola
March 2001
doc.: IEEE 802.15-01/135r1
Criteria 4
20. What is the range requirement of
the application?
10cm to 10m is
1-30 m
typical; 10m to
100m with
tradeoffs is
desirable
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
product
Coexistence
Technical Feasibility
MD
demonstrated
in hardware
Global Utility
yes
Submission
Slide 18
Ed Callaway, Motorola