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1. (WO2007007226) METHOD, COMMUNICATION SYSTEM AND COMMUNICATION UNIT FOR PROTECTING INCUMBENT WIRELESS SERVICES
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

METHOD, COMMUNICATION SYSTEM AND COMMUNICATION UNIT FOR PROTECTING INCUMBENT WIRELESS SERVICES

The invention relates to a Method for protecting incumbent services whereas in the incumbent services first information is exchanged between first communication means by radio frequency transmission within a first bandwidth using a first protocol and second information is exchanged between second communication means by radio frequency transmission within a second bandwidth using a second protocol and the second bandwidth is overlapping and larger than the first bandwidth.
The invention relates also to a Communication system for protecting incumbent services whereas a incumbent service uses first communication means for exchanging first information by radio frequency transmission within a first bandwidth using a first protocol and whereas the communication system includes second communication means for exchanging second information between second
communication means by radio frequency transmission within a second bandwidth using a second protocol and the second bandwidth is overlapping and larger than the first bandwidth.
The invention further relates to a Communication unit for protecting incumbent services whereas a incumbent service uses first communication means for exchanging first information by radio frequency transmission within a first bandwidth using a first protocol and for communication with a second information exchange between second communication means as one of the communication means for exchanging second information between second communication means by radio frequency transmission within a second bandwidth using a second protocol and the second bandwidth is overlapping and larger than the first bandwidth.
New wireless applications (so-called secondary services) are coming up that reuse spectrum that is already allocated for other applications, the so-called incumbent (or primary) services. Examples are WLAN (Wireless LAN) in the 5 GHz band and UWB (Ultra Wideband). Since the incumbent services are typically licensed and the new application license exempt, the former need to be protected from interference by the latter. This is particular complicated for UWB, which may operate from 3.1 to 10.6 GHz, since many incumbent services may be affected.

The US Patent Application 2004/0199686 Al relates to a wireless communication of communication devices within a piconet. Particularly it relates for avoiding an interference of competing devices within the piconet. This publication does not solve the above mentioned problem.
The US Patent Application 2005/0083896 Al describes the coexistence of multiple piconets such as UWB. This description does not eliminate any interference to other nets or wireless services.
The GB Patent 2399475 A relates to avoidance of interference between cellular phone network and UWB. This is solved by a time division.
A scheme to distribute regulatory information such as allowed channels and maximum transmit power is described in IEEE 802.1 ld-2001 : Specification for Operation in Additional Regulatory Domains
(http://standards.ieee.org/getieee802/download/802.l ld-2001.pdf).
A scheme to protect radars, which are important incumbent services in the 5 GHz band, from WLAN interference, is described in IEEE 802.1 lh-2003:
Spectrum and Transmit Power Management Extensions in the 5GHz band in Europe (http://standards.ieee.org/getieee802/download/802.l lh-2003.pdf).
The MBOA proposed UWB system is described in IEEE P802.15-04/0493rl : "Multi-band OFDM Physical Layer Proposal for IEEE 802.15 Task Group

3a" (ftp://ieee:wireless@ftp.802wirelessworld.com/15/04/15-04-0493-01-003a-multi-band-ofdm-cfp-document-update.zip).
In order to obtain a useful range, UWB systems need to operate at transmit power levels (the FCC allows →41.3 dBm/MHz) that might cause interference to incumbent services in certain situations.

The problem to be solved is to reduce or to eliminate an interference of secondary services to incumbent services.
The problem is solved by a method according to claim 0. Preferred versions of the method are claimed in claims 2 to 10.
The problem is also solved by a communication system according to claim 11. Preferred embodiments of the communication system are claimed in claims 12 to 20.
The problem is also solved by a communication unit according to claim 21. Preferred embodiments are claimed in claims 22 to 29.
In order to obtain a useful range secondary services for exchanging first information need to operate at transmit power levels that might cause interference to incumbent services exchanging second information in certain situations.
Typically, the secondary service uses a bandwidth that is multiple larger than the incumbent service, so the interference can be much reduced if the secondary service avoids to transmit in the small band used by the incumbent service (notching), without significant reduction of the secondary service performance.
A problem is to know which frequencies have to be notched. The autodetection of some incumbent services, e.g. the downlink of fixed wireless access, is very difficult due to the low receiving signal levels.
This invention overcomes the autodetection problem by introducing a new signalling scheme that is used to "tell" second communication means which frequencies have to be notched. It is assumed that at least one of the second
communications means, e.g. in a UWB piconet, is rather stationary, e.g. a PC or TV set, so it is able to know the local incumbent services to be protected and it distributes this information to the other second communication means.
It is expected that at least one of the second communication means "knows" the protection information. Possibilities where this knowledge is coming from are factory configuration, autodetection or hand configuration by the user.

In the following the invention is described by an example. In the drawings shows Fig. 1 a Subcarrier range format and
Fig. 2 a 2 — Protection Information Element format.

For sencondary services there are several UWB protocols proposed. This invention is applicable to all of these.
As example embodiment, the WiMedia/MBOA MAC protocol is chosen (MBOA Draft MAC Standard 0.95, April 11, 2005).
In section 7.8 of this standard, several information elements (IEs) are specified that may be present in management frames. In order to implement this invention, a new IE "Protection IE" has to be added, which shall be used in Beacon and

Probe Response frames if protection information is available.
Since WiMedia/MBOA is based on OFDM, it is preferable to specify frequency ranges in OFDM subcarrier numbers instead of absolute frequencies as shown in Fig. 1. The frequency (f) / subcarrier (n) relation can be defined as

f = 3168 MHz + n * 4.125 MHz, where n = 0, 1, ..., 1792.

Subcarriers from nlower to nupper shall be nulled (notched).
For non-OFDM systems, it is preferable to specify frequency ranges in absolute frequencies.
Fig. 2 shows a 2 — Protection Information Element format. The terminal as communication means receiving this Information Element shall avoid transmitting on all subcarrieres specified in the Subcarrier Range List.
A possible Protection Information Element format is given in Figures 1 and 2.
A further advantage of this invention is that the notching information can also be used by the receiver, which can improve its decoding performance by ignoring the notched subcarriers.
A major application for UWB is expected to be WUSB, the wireless extension of USB. As wired USB, this application is PC centric, so in many cases it will be controlled by a stationary desktop PC, which is likely to know the local incumbent services to be protected.