Anritsu HFE0104 TechRept

36 High Frequency Electronics From January 2004 High Frequency Electronics

Copyright © Summit Technical Media, LLC

T

his report offers a brief summary of some recent
activities in wireless system standards. The

standards process is continuous—even estab­lished standards are updated and modified in response
to changes in technology and marketplace. It is impos­sible to collect comprehensive data on all standards.
This update is just a snapshot of a few standards we
think are of current interest to our readers.

IEEE 802.15.4 WPAN Standard

IEEE 802.15.4 is the IEEE standard, covering
Wireless Personal Area Networks (WPAN), which was
approved and published in late 2003. It defines a phys­ical layer (PHY) and media access controller (MAC) for
applications in home networking, automotive net­works, industrial networks, interactive toys and
remote metering.

The standard provides for data rates of 250 kbps,
40 kbps and 20 kbps in a star or peer-to-peer configu­ration. It has dynamic device addressing and a fully
handshaked protocol for transfer reliability. Frequency
bands are 16 channels in the 2.4 GHz ISM band, 10
channels in the 915 MHz ISM band and one channel in
the European 868 MHz band. Key attributes of

802.15.4 include:

2.4 GHz PHY

• 250 kbps (4 bits/symbol, 62.5 ksymbols/s)

• Data modulation is 16-ary orthogonal modulation

• 16 symbols are orthogonal set of 32-chip PN codes

• Chip modulation is O-QPSK at 2.0 Mchips/s

868 MHz/915 MHz PHY

• Symbol Rate

868 MHz Band: 20 kbps

(1 bit/symbol, 20 ksymbols/s)

915 MHz Band: 40 kbps

(1 bit/symbol, 40 ksymbols/s)

• Data modulation is BPSK with differential encoding

• Spreading code: a 15-chip m-sequence

• Chip modulation is BPSK:

868 MHz Band: 300 kchips/s

915 MHz Band: 600 kchips/s

• Transmit Power: at least 0.5 mW

• Transmit Center Frequency Tolerance: ± 40 ppm

• Receiver Sensitivity (Packet Error Rate <1%):
<-85 dBm @ 2.4 GHz band
<-92 dBm @ 868/915 MHz band

This standard is designed for very low power con­sumption, low cost and complexity, but with reliable
data transfer. The specific implementations may vary
from intermittent data (e.g. an appliance on/off con­troller) to continuous, but low rate data (e.g. a cordless
mouse or a periodically polled sensor).

The application areas of 802.15.4 overlap with
Bluetooth, Zigbee, Home RF and other short-range
wireless data transmission systems.

The differences with Bluetooth are often described
as market-based—Bluetooth products are mainly tar­geted to individual users, operating primarily in con­junction with cellular handsets, personal computers
and PDAs. 802.15.4 is intended for a wider range of
applications, including both larger networks and inter­facing with devices that are not part of existing net­works or systems.

Zigbee is designed for even lower power consump­tion and lower cost implementation. It also is designed
for less flexible operation, emphasizing master-slave
relationships in an environment such as an in-build­ing HVAC control system. As part of the cost-savings,
Zigbee specifies direct sequence spread spectrum
(DSSS) rather than 802.15.4’s frequency hopping
(FHSS). 802.15.4 allows for data rates two to four
times higher than Zigbee’s 128 kbps.

The IEEE WPAN standard establishes a means for
short-range wireless communications with the inter­operability necessary for marketplace acceptance, with
more flexibility than other standards that are focused
on a narrower range of applications.

At least eight chip makers have announced prod­ucts compliant with 802.15.4, which should encourage
hardware developers to proceed with their planned
short-range data products.

TECHNOLOGY REPORT

An Update on Wireless
Standards Activity

38 High Frequency Electronics

Ultra Wideband (UWB)

One of the points of contention among proponents
of various ultra wideband transmission standards is
the use of orthogonal frequency domain modulation
(OFDM). IEEE standard 802.15.3a for multiband
OFDM (MB-OFDM) was released as a draft specifica­tion in November 2003.

Multi-Band OFDM Alliance (MBOA), a UWB
industry group, has stated that they will generate
specifications based on the IEEE proposal, as version

0.9 in February 2004 and 1.0 in May 2004. Although
the MBOA supports the IEEE process, it will be work­ing in parallel to help speed time-to-market. The
MBOA has nearly one hundred engineers from about
30 companies working within 8 technical subcommit­tees to define the specification.

There is concern that an OFDM-based standard
would not comply with FCC regulations. Xtreme
Spectrum, one of the pioneers in UWB development
also has a proposal for the 802.15.3a wireless net­working standard. The Xtreme Spectrum proposal
uses a direct sequence code division multiple access
(DS-CDMA) approach. To avoid another area of con­cern—IP licensing—Xtreme has said that it will offer
“reasonable and non-discriminatory zero licensing”
(RAND-Z) access to its intellectual property (IP) rele­vant to the standard.

802.16 Wireless Broadband

The 802.16 metropolitan area network (MAN)
standard was released in april 2003, but continues to
draw interest in product and system development, as
well draw controversy on its role in the wireless land­scape that also includes 802.11 technologies.

Current activities include draft releases of updates
and amendments for the air interface, PHY and MAC
layer details for the lower frequencies (2 to 11 GHz),
plus protocol conformance and test suite definitions for
the higher frequencies (10-66 GHz).

802.16 has evolved greatly from its initial 1999
focus on local multipoint distribution service (LMDS).
It now includes features that overlap and/or comple­ment portions of the 802.11 standard. For the under-11
GHz range, 802.16 can be characterized as “broadband
wireless” that is aimed at infrastructure applications
rather than the “last 100 feet” of 802.11 WLAN. The
overlap occurs in applications where 802.16 is
designed to the home rather than as a backbone with

802.11 as the individual access format.

The 802.16a standard specifies three physical lay­ers for services: a single-carrier access method for spe­cial-purpose networks; a 256-carrier orthogonal fre­quency division multiplexed (OFDM) multicarrier
PHY for mainstream applications; and a special
OFDMa with 2,048 carriers, which can be used for

selective multicast applications, and advanced multi­plexing options.

The 802.16 Task Group C for 10- to 66-GHz fre­quency ranges continues to work on higher-frequency
services evolving from LMDS and point-to-point 50- to
60-GHz radio. After some well-publicized failures of
early LMDS efforts, 802-16-based broadband wireless
access (BWA) is again starting to grow in investment
and public awareness. Some 802.11-based wireless
access providers have been sufficiently successful to be
considered small-scale examples of the kind of service
that BWA can provide where cable and DSL are not
presently available.

802.16-based systems are getting lots of interna­tional attention. As with cellular telephony, the lack of
wired infrastructure in many parts of the world cre­ates potential markets for wireless distribution.
China, Korea, Russia and several Eastern European
countries have been mentioned as key places with an
interest in wireless broadband distribution.

Digital Television in Europe

In conjunction with ETSI, CENELEC is undertak­ing the process of defining further standardization in
interactive digital television. As directed by the
European Commission, working groups have been
identifying existing standardization initiatives at
international, European and national levels, both for­mal and informal, and identifying gaps requiring fur­ther standardization work. Under its Framework
Directive 2002/21/EC, the EU has laid down a tight
timescale for the Commission to review the interoper­ability of digital TV interactive services. Following a
consultation document scheduled for publication in
December 2003, the Commission is due to deliver a for­mal assessment of the state of play regarding interop­erability no later than July 2004.

CENELEC Adds New Members

Coinciding with the beginning of a new year, CEN­ELEC now has four new members. The National
Electrotechnical Committees of Estonia, Latvia,
Poland and Slovenia joined CENELEC on this date.
These four countries join now a list that includes the
Czech Republic (member since 1997), Malta (2001)
Hungary and Slovakia (2002) and Lithuania (2003),
completing the enlargement to the East even before
the target date. With the four newcomers, CENELEC
will reach 27 members. One of the consequences of the
enlargement will be the adoption, also from January
1st 2004, of the weighted votes agreed by the
European Union in the Treaty of Nice. CENELEC
hopes and expects Cyprus to become the 28th member
before May 2004, completing this way the objectives
set out by the European Commission.

TECHNOLOGY REPORT