Technique for effectively utilizing bandwidth of a cable network for ...

(54) TECHNIQUE FOR EFFECTIVELY

UTILIZING BANDWIDTH OF A CABLE
NETWORK FOR WIRELESS
COMMUNICATIONS

(75) Inventor: George Philip Vella-Coleiro, Summit, NJ (US)

(73) Assignee: Lucent Technologies Inc., Murray Hill, NJ (US)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/042,478

(22) Filed: Mar. 16, 1998

(51) Int. CI.7 H04B 1/40; H04B 7/216

(52) U.S. CI 370/342; 455/75

(58) Field of Search 370/295, 488,

370/485, 486, 487, 497, 342; 455/5.1, 75, 161.2, 164.2; 375/295

(56) References Cited

U.S. PATENT DOCUMENTS

4,272,743 A * 6/1981 Evans 333/176

4,321,706 A * 3/1982 Craft 375/59

In a cable network for delivering a personal communications service (PCS) and cable television (CATV) service, return service applications, e.g., a pay per view service, are also provided on a return cable band provided by the cable network. In accordance with the invention, the return service applications utilize subbands unused by the PCS in the return cable band, thereby unaffecting the PCS. The broadband noise in the subbands normally accompanied by the PCS is filtered out using a tunable filter whose passband is adjustable to coincide with one of many PCS signal bands being used in the return cable band.

25 Claims, 2 Drawing Sheets

1

TECHNIQUE FOR EFFECTIVELY
UTILIZING BANDWIDTH OF A CABLE
NETWORK FOR WIRELESS
COMMUNICATIONS

5

FIELD OF THE INVENTION

The invention relates to communications systems and methods, and more particularly to a system and method for wireless communications using bandwidth of a cable net- 10 work.

BACKGROUND OF THE INVENTION

Because of the popularity of cable television (CATV), cable networks for transporting CATV signals to CATV 15 subscriber premises proliferate at a rapid pace. Taking advantage of the broad band provided by a cable network, telephone companies deliver wireless telephony services, e.g., a personal communications service (PCS), through the network. For example, the cable network affords a commu- 20 nication medium between a base station and cable microcell integrators (CMIs) connected thereto for providing the PCS. A CMI is typically mounted on a cable trunk in the cable network, and includes antennas for transmitting and receiving in a wireless manner communication information to and 25 from mobile terminals, e.g., radiotelephones, subscribing to the PCS. The base station performs call administration, and establishes and maintains telephone connections between the mobile terminals and other communication terminals, which may or may not be mobile terminals, via, e.g., a public 30 switched telephone network (PSTN).

After a telephone connection is established between a communication terminal and a mobile terminal, the base station generates a transmit signal representative of digital information from the communication terminal, in accor- 35 dance with the PCS standard and a well known multiple access technique, e.g., a code division multiple access (CDMA) technique. The base station sends the transmit signal, through a forward cable band (450 MHz-750 MHz) provided by the cable network, to the CMIs where the digital 40 information is transmitted to the mobile terminal. In the reverse direction, the CMIs receive digital information from the mobile terminal, and send multiple reverse PCS CDMA signals containing the received information, through a return cable band (5 MHz-42 MHz) provided by the cable 45 network, to the base station where the information is transmitted to the communication terminal, thereby realizing duplex communications.

Recently, a number of applications emerged, known as "return service applications," which need to also utilize the 50 return cable band to provide, e.g., pay per view services, Internet access, interactive games, etc. Although the reverse PCS CDMA signals do not fully populate the 5 MHz-42 MHz return cable band, thus leaving unused bandwidth therein, the return service applications, however, cannot take 55 advantage of such unused bandwidth as the whole return cable band is corrupted by broadband noise entering through the CMIs.

An effort has been made to make available bandwidth in the return cable band to accommodate the return service 60 applications. This effort involves use of a bandpass filter to limit the band for the reverse PCS CDMA signals to only 5 MHz through 18 MHz, thereby affording the remaining return cable band 18 MHz through 42 MHz to the return service applications. However, such an effort is ineffective 65 as the return service applications are accommodated at the expense of the PCS, thereby adversely affecting the PCS.

2

Accordingly, there exists a need for a methodology for effectively locating bandwidth in a return cable band of a cable network for return service applications, without adversely affecting the PCS.

SUMMARY OF THE INVENTION

I have recognized that because of use of the CDMA technique in the PCS described above, even though the reverse PCS communication is active, the power spectrum of the reverse CDMA PCS signals, including their power level, resemble that of pure channel noise as if no communication were going on. In other words, a pure-channelnoise-like signal, referred to as a "pedestal noise signal," always appears in a signal band being used for the PCS in the return cable band, regardless of whether the reverse PCS communication is active. I have also recognized that the power level of the pedestal noise signal is significantly higher than that of the broadband noise corrupting the return cable band.

Thus, in accordance with the invention, the pedestal noise signal is detected to identify the signal band being used for the PCS. Such detection may be based on a significant rise in the power level in a transition from the broadband noise to the pedestal noise signal in the return cable band. A tunable filter is used, whose passband is controllably adjusted to cover the identified signal band, to filter out the noise in the rest of the return cable band.

Advantageously, with the invention, the bandwidth unused by the PCS in the return cable band, which is noise-free, can be allocated to the return service applications, without affecting the PCS.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing,

FIG. 1 is a block diagram of a cable network arrangement in accordance with the invention;

FIG. 2 is a block diagram of a cable microcell integrator facility used in the arrangement of FIG. 1; and

FIG. 3 illustrates a signal power spectrum in a return cable band provided by the cable network arrangement of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates cable network arrangement 100 embodying the principles of the invention for delivering a wireless telephony service, e.g., a personal communications service (PCS) in this instance, and return service applications described below in addition to a conventional cable television (CATV) service.

In FIG. 1, cable headend 103 is connected to cable microcell integrator (CMI) facilities 121 and 123 through a hybrid fiber cable (HFC) plant, including optical fibers 113a and 113fc, fiber node 105 and coaxial cable 117. CMI facilities 121 and 123 in accordance with the invention are fully described below. However, it suffices to know for now that facilities 121 and 123 are mounted on cable 117, and include antennas for transmitting and receiving in a wireless manner communication information to and from mobile terminals, e.g., radiotelephones, within a pre-defined geographic coverage. As is well known, a PCS service area is divided into a multiplicity of cells, and each cell typically is further divided into a number of sectors. Although arrangement 100 may be used to serve mobile terminals in one such cell, without loss of generality, only the components in arrangement 100 corresponding to the service of one such sector in the cell are shown in FIG. 1. Thus, the aforementioned pre-defined geographic coverage in this instance is such a sector.