1. TIM Broadcast r4 Date: 2007-07-14 Menzo Wentink, et. al. Author(s):
Name
Company
Address
Phone
Menzo Wentink
Conexant
Oudegracht 3, Utrecht, Netherlands
Bob O´Hara
Cisco Systems
3625 Cisco Way, San Jose, CA
Allen Thomson
170 W Tasman, San Jose, CA
Jari Jokela
Nokia
Visiokatu 1, Tampere, Finland
Marc de Courville
Motorola
Parc les Algorithmes, Gif-sur-Yvette, France
Sanjiv Nanda
Qualcomm
5775 Morehouse Drive, San Diego, CA, USA
Ian Sherlock
Texas Instruments
12500 TI Blvd, Dallas, TX, USA
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Menzo Wentink, et. al.

2. Changes to Normative Text for r2 to r3
A request/response handshake was added, where stations can request for a particular TIM broadcast interval (in units of Beacon Periods)
The high rate and low rate TIMs are transmitted back to back (SIFS separated) at a single offset
The high rate TIM is now optional in 5 GHz, because the low rate TIM is already transmitted in OFDM
Menzo Wentink, et. al.

3. r4
Introduction
TIM Broadcast is a mechanism to receive the TIM field with as little overhead as possible
To this end, the AP transmits two TIM frames per beacon period
one TIM at the same rate as the Beacon
one TIM at a higher rate which is not DSSS (i.e. OFDM)
TIM Broadcast has advantage over receiving a Beacon or a Probe Request:
2,000 us Beacon at 1 Mbps
36 us TIM frame at 24 Mbps
The actual gain in power saving depends on implementation specific factors like sleep/Rx ratio, ramp up time, DTIM period, etc.
very large reduction in power consumption is feasible
Menzo Wentink, et. al.

4. New Action Frame and IE TIM Action Frame TIM Broadcast IE r4 Category
Check Beacon
TIM
Octets: 1
6-257
TIM Action Frame
Element ID
Length
TIM
Offset 1
Rate 1 …
Offset n
Rate n
Octets: 1 2
TIM Broadcast IE
Menzo Wentink, et. al.

5. r4
Overhead
The overhead for transmitting TIM Broadcasts is about 650 us, including SIFS and DIFS. For a TIM interval of 3, this implies that the overhead would be 0.2%
Menzo Wentink, et. al.