Transcript 19-05-0026-00-0000_Cordless_Telephone_Coexistence_Considerations.ppt

July 2005
doc.: IEEE 802.19-05/0026r0
Cordless Telephone
Coexistence Considerations
Date: 2005-07-20
Authors:
Name
Company
Address
Phone
email
Stephen R
Whitesell
VTech
Communications
2 Shannon Ct
Howell, NJ 07731
732 751 1079
[email protected]
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Submission
Slide 1
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
Abstract
Basic characteristics of cordless telephones operating in
the unlicensed 2.4 and 5.8 GHz ISM bands are discussed.
Coexistence analyses of proposed IEEE 802 standards
that include operation in these bands should take these
characteristics into account.
Submission
Slide 2
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
Cordless Telephone Technologies
• Analog
• Digital
– Frequency Hopping Spread Spectrum (FHSS)
– Direct Sequence Spread Spectrum (DSSS)
– Other Digital Modulation Techniques
Submission
Slide 3
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
Analog Telephones Operating under
Part 15.249 of the FCC Rules
• Frequency Bands
– 2.4 GHz (2400 to 2483.5 MHz)
– 5.8 GHz (5725 to 5875 MHz)
• Field Strength
– 50 mV/m measured at 3 m
• Other Characteristics
–
–
–
–
Submission
Narrow band FM
Paired handset and base transmitting on separate frequencies
Multiple frequencies available, but only one pair in use at a time
Changes frequencies to avoid interference
Slide 4
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
Digital Telephones Operating under
Part 15.247 of the FCC Rules
• Frequency Bands
– 2.4 GHz (2400 to 2483.5 MHz)
– 5.8 GHz (5725 to 5850 MHz)*
• Power
– Limit is 1.0 W, except
– Limit for 2.4 GHz FHSS using less than 75 channels is 0.125 W
– Typical is 0.25 W or less
• Other Characteristics
– Depends on modulation method and (sometimes) on frequency
band
* 5.8 GHz upper band limit for digital under Part 15.249 is 25 MHz lower than for analog under Part 15.247
Submission
Slide 5
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
FHSS Systems using WDCT* Chipsets
• Characteristics
– 95 channels, 864 kHz spacing, 800 kHz typical bandwidth
– 75 channels in hop set, 20 reserve channels can be swapped out
– TDD system with eight 1.25 ms time slots per 10 ms frame
(four TX slots and four RX slots)
– 100 Hz hop rate (1 frame per hop)
– Supports simultaneous use of up to four handsets
• Alternative Characteristics for “WiFi Aware” Phones
– Reduced number of channels in hop set, 17 typical
– Allowed only in 2.4 GHz band
* Worldwide Digital Cordless Telecommunications
Submission
Slide 6
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
WDCT Time Slot Assignments
Base Transmit, Handset Receive
TS0
TS1
TS2
Handset Transmit, Base Receive
TS3
TS4
TS5
TS6
TS7
1.25 ms
10 ms
Submission
Slide 7
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
WDCT Operation
• Base unit uses TS0 to transmit a dummy bearer or
beacon signal.
• Slots TS3 & TS7 are used as the traffic bearers for the
first handset engaged, TS2 & TS6 for the second
handset, TS1 & TS5 for the third handset, and TS0 and
TS4 for the fourth handset. TS0 carries both beacon
signal and traffic for fourth handset if four handsets
are engaged.
• Traffic moves to higher numbered slots as handsets
become disengaged. That is, TS3 & TS7 are always
used by handset that has been engaged longest.
Submission
Slide 8
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
FHSS WDCT 2-Handset Example
0.5 to 30 m
Typical
Hdst 1
Transmits
on TS7
Submission
Up to 100 m
Possible
Base
Transmits on
TS0, TS2, TS3
Hdst 2
Transmits
on TS6
Slide 9
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
WDCT Coexistence Mechanisms
• Swap out channels on which interference is detected.
• “WiFi Aware” 2.4 GHz telephones will try moving to
another area of the band if an 802.11b or 802.11g
WLAN is detected.
Submission
Slide 10
Stephen R Whitesell, VTech Communications
July 2005
doc.: IEEE 802.19-05/0026r0
References
• FCC Part 15 Rules
Submission
Slide 11
Stephen R Whitesell, VTech Communications