Source: https://patents.google.com/patent/US10264562B2/en
Timestamp: 2020-01-21 18:25:35
Document Index: 487105259

Matched Legal Cases: ['§ 311', '§ 42', '§ 311', '§ 42', '§ 311', '§ 42']

US10264562B2 - TDD FDD communication interface - Google Patents
TDD FDD communication interface Download PDF
US10264562B2
US10264562B2 US13/532,650 US201213532650A US10264562B2 US 10264562 B2 US10264562 B2 US 10264562B2 US 201213532650 A US201213532650 A US 201213532650A US 10264562 B2 US10264562 B2 US 10264562B2
US13/532,650
US20120263079A1 (en
2001-01-19 Priority to US26282701P priority Critical
2007-10-31 Priority to US11/982,404 priority patent/US20080261588A1/en
2012-06-25 Priority to US13/532,650 priority patent/US10264562B2/en
2012-06-25 Application filed by Access Solutions Ltd filed Critical Access Solutions Ltd
2012-10-18 Publication of US20120263079A1 publication Critical patent/US20120263079A1/en
2019-04-16 Publication of US10264562B2 publication Critical patent/US10264562B2/en
TDD access equipment modified by introducing a frequency change at the normal TDD guard point, with respective downlink or uplink periods for individual subscriber stations offset to form overlapping frames. Cyclo-stationary processing, block equalization, and burst timing coordination allow the boundary between downlink and uplink portions of both frames to be set dynamically, improving spectral efficiency. Fast frequency switching within an allotted physical slot enables synchronization of time-sharing the dedicated frequencies to be maintained among subscriber stations. Duplex spacing between downlink and uplink frequencies for individual subscriber stations, combined with in-depth filtering of received signals, prevents spurious out-of-band transmission signal strength from reaching an interference level.
This application is a continuation of prior U.S. patent application Ser. No. 11/982,404 filed on Oct. 31, 2007 now abandoned, which claims priority to: U.S. patent application Ser. No. 09/839,499 filed on Apr. 20, 2001, now U.S. Pat. No. 7,346,347. U.S. patent application Ser. No. 09/839,499 claims priority to provisional U.S. Patent Application Ser. No. 60/262,708 filed on Jan. 19, 2001 and U.S. patent application Ser. No. 09/713,684 filed on Nov. 15, 2000.
This application claims priority to: provisional U.S. Patent Application Ser. No. 60/262,712 filed on Jan. 19, 2001 and entitled “WIRELESS COMMUNICATION SYSTEM USING BLOCK FILTERING AND FAST EQUALIZATION DEMODULATION AND METHOD OF OPERATION”; provisional U.S. Patent Application Ser. No. 60/262,825 filed on Jan. 19, 2001 and entitled “APPARATUS AND ASSOCIATED METHOD FOR OPERATING UPON DATA SIGNALS RECEIVED AT A RECEIVING STATION OF A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”; provisional U.S. Patent Application Ser. No. 60/262,698 filed on Jan. 19, 2001 and entitled “APPARATUS AND METHOD FOR OPERATING A SUBSCRIBER INTERFACE IN A FIXED WIRELESS SYSTEM”; provisional U.S. Patent Application Ser. No. 60/262,827 filed on Jan. 19, 2001 entitled “APPARATUS AND METHOD FOR CREATING SIGNAL AND PROFILES AT A RECEIVING STATION”; provisional U.S. Patent Application Ser. No. 60/262,826 filed on Jan. 19, 2001 and entitled “SYSTEM AND METHOD FOR INTERFACE BETWEEN A SUBSCRIBER MODEM AND SUBSCRIBER PREMISES INTERFACE”; provisional U.S. Patent Application Ser. No. 60/262,951 filed on Jan. 19, 2001 entitled “BACKPLANE ARCHITECTURE FOR USE IN WIRELESS AND WIRELINE ACCESS SYSTEMS”; provisional U.S. Patent Application Ser. No. 60/262,824 filed on Jan. 19, 2001 entitled “SYSTEM AND METHOD FOR ON-LINE INSERTION OF LINE REPLACEABLE UNITS IN WIRELESS AND WIRELINE ACCESS SYSTEMS”; provisional U.S. Patent Application Ser. No. 60/263,101 filed on Jan. 19, 2001 entitled “SYSTEM FOR COORDINATION OF TDD TRANSMISSION BURSTS WITHIN AND BETWEEN CELLS IN A WIRELESS ACCESS SYSTEM AND METHOD OF OPERATION”; provisional U.S. Patent Application Ser. No. 60/263,097 filed on Jan. 19, 2001 and entitled “REDUNDANT TELECOMMUNICATION SYSTEM USING MEMORY EQUALIZATION APPARATUS AND METHOD OF OPERATION”; provisional U.S. Patent Application Ser. No. 60/273,579 filed Mar. 5, 2001 and entitled “WIRELESS ACCESS SYSTEM FOR ALLOCATING AND SYNCHRONIZING UPLINK AND DOWNLINK OF TDD FRAMES AND METHOD OF OPERATION”; provisional U.S. Patent Application Ser. No. 60/262,955 filed Jan. 19, 2001 and entitled “TDD FDD AIR INTERFACE”; provisional U.S. Patent Application Ser. No. 60/262,708 filed on Jan. 19, 2001 and entitled “APPARATUS, AND AN ASSOCIATED METHOD FOR PROVIDING WLAN SERVICE IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”; provisional U.S. Application Ser. No. 60/273,689 filed on Mar. 5, 2001 and entitled “WIRELESS ACCESS SYSTEM USING MULTIPLE MODULATION FORMATS IN TDD FRAMES AND METHOD OF OPERATION”; provisional U.S. Patent Application Ser. No. 60/273,757 filed Mar. 5, 2001 and entitled “WIRELESS ACCESS SYSTEM AND ASSOCIATED METHOD USING MULTIPLE MODULATION FORMATS IN TDD FRAMES ACCORDING TO SUBSCRIBER SERVICE TYPE”; provisional U.S. Patent Application Ser. No. 60/270,378 filed Feb. 21, 2001 and entitled “APPARATUS FOR ESTABLISHING A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”; provisional U.S. Patent Application Ser. No. 60/270,385 filed Feb. 21, 2001 and entitled, “APPARATUS FOR REALLOCATING COMMUNICATION RESOURCES TO ESTABLISH A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”; and provisional U.S. Patent Application Ser. No. 60/270,430 filed Feb. 21, 2001 and entitled “METHOD FOR ESTABLISHING A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM. Each of these applications and/or patents are hereby incorporated by reference herein in their entireties.
2) Ser. No. 09/838,810 filed Apr. 20, 2001, and entitled “WIRELESS COMMUNICATION SYSTEM USING BLOCK FILTERING AND FAST EQUALIZATION-DEMODULATION AND METHOD OF OPERATION”, now U.S. Pat. No. 7,075,967;
3) Ser. No. 09/839,726 filed Apr. 20, 2001, and entitled “APPARATUS AND ASSOCIATED METHOD FOR OPERATING UPON DATA SIGNALS RECEIVED AT A RECEIVING STATION OF A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”, now U.S. Pat. No. 7,099,383;
4) Ser. No. 09/839,729 filed Apr. 20, 2001, and entitled “APPARATUS AND METHOD FOR OPERATING A SUBSCRIBER INTERFACE IN A FIXED WIRELESS SYSTEM”, abandoned;
5) Ser. No. 09/839,719 filed Apr. 20, 2001, and entitled “APPARATUS AND METHOD FOR CREATING SIGNAL AND PROFILES AT A RECEIVING STATION”, now U.S. Pat. No. 6,947,477;
6) Ser. No. 09/838,910 filed Apr. 20, 2001, and entitled “SYSTEM AND METHOD FOR INTERFACE BETWEEN A SUBSCRIBER MODEM AND SUBSCRIBER PREMISES INTERFACES”, now U.S. Pat. No. 6,564,051;
8) Ser. No. 09/839,514 filed Apr. 20, 2001, and entitled “SYSTEM AND METHOD FOR ON-LINE INSERTION OF LINE REPLACEABLE UNITS IN WIRELESS AND WIRELINE ACCESS SYSTEMS”, now U.S. Pat. No. 7,069,047;
9) Ser. No. 09/839,512 filed Apr. 20, 2001, and entitled “SYSTEM FOR COORDINATION OF TDD TRANSMISSION BURSTS WITHIN AND BETWEEN CELLS IN A WIRELESS ACCESS SYSTEM AND METHOD OF OPERATION”, now U.S. Pat. No. 6,804,527;
10) Ser. No. 09/839,259 filed Apr. 20, 2001, and entitled “REDUNDANT TELECOMMUNICATION SYSTEM USING MEMORY EQUALIZATION APPARATUS AND METHOD OF OPERATION”, now U.S. Pat. No. 7,065,098;
11) Ser. No. 09/839,457 filed Apr. 20, 2001, and entitled “WIRELESS′ACCESS SYSTEM FOR ALLOCATING AND SYNCHRONIZING UPLINK AND DOWNLINK OF TDD FRAMES AND METHOD OF OPERATION”, now U.S. Pat. No. 7,002,929;
12) Ser. No. 09/839,075 filed Apr. 20, 2001, and entitled “TDD FDD AIR INTERFACE”, now U.S. Pat. No. 6,859,655;
13) Ser. No. 09/839,458 filed. Apr. 20, 2001, and entitled “WIRELESS ACCESS SYSTEM USING MULTIPLE MODULATION FORMATS IN TDD FRAMES AND METHOD OF OPERATION”, now U.S. Pat. No. 7,173,916;
14) Ser. No. 09/839,456 filed Apr. 20, 2001, and entitled “WIRELESS ACCESS SYSTEM AND ASSOCIATED METHOD USING MULTIPLE MODULATION FORMATS IN TDD FRAMES ACCORDING TO SUBSCRIBER SERVICE TYPE”, now U.S. Pat. No. 6,891,810;
15) Ser. No. 09/838,924 filed Apr. 20, 2001, and entitled “APPARATUS FOR ESTABLISHING A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”, now U.S. Pat. No. 7,274,946;
16) Ser. No. 09/839,727 filed Apr. 20, 2001, and entitled “APPARATUS FOR REALLOCATING COMMUNICATION RESOURCES TO ESTABLISH A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”, now U.S. Pat. No. 7,031,738;
17) Ser. No. 09/839,734 filed Apr. 20, 2001, and entitled “METHOD FOR ESTABLISHING A PRIORITY CALL IN A FIXED WIRELESS ACCESS COMMUNICATION SYSTEM”, now U.S. Pat. No. 7,035,241;
18) Ser. No. 09/839,513 filed Apr. 20, 2001, and entitled “SYSTEM AND METHOD FOR PROVIDING AN IMPROVED COMMON CONTROL BUS FOR USE IN ON-LINE INSERTION OF LINE REPLACEABLE UNITS IN WIRELESS AND WIRELINE ACCESS SYSTEMS”, now U.S. Pat. No. 6,925,516; and
19) Ser. No. 09/948,059, filed Sep. 5, 2001, and entitled “WIRELESS ACCESS SYSTEM USING SELECTIVELY ADAPTABLE BEAM FORMING IN TDD FRAMES AND METHOD OF OPERATION”, now U.S. Pat. No. 7,230,931.
The present disclosure is directed, in general, to communication network access systems and, more specifically, to access equipment for use in both wireless and wireline telecommunications systems.
By the late 1980s, the limitations of data modem connections over voice frequency (VF) pairs were becoming obvious to both subscribers and telecommunications service providers. ISDN (Integrated Services Digital Network) was introduced to provide universal 128 kbps service in the access network. The subscriber interface is based on 64 kbps digitization of the VF pair for digital multiplexing into high speed digital transmission streams (e.g. t TI/T3 lines in North America t E1/E3 lines in Europe). ISDN was a logical extension of the digital network that had evolved throughout the 1980s. The rollout of ISDN in Europe was highly successful. However, the rollout in the United States was not successful t due in part to artificially high tariff costs which greatly inhibited the acceptance of ISDN.
1) Relatively high hit error rates (BER) compared to wire line or optical systems; and
b) Class 5 switch interfaces (domestic GR-303 and international VS.2);
Unlike physical optical or wire systems that operate at bit error rates (BER) of 10-11, wireless access systems have time varying channels that typically provide bit error rates of 10-3 to 10-6. The wireless physical (PHY) layer interface and the media access control (MAC) layer interface must provide modulation, error correction and ARQ protocol that can detect and, where required, correct or retransmit corrupted data so that the interfaces at the network and at the subscriber site operate at wire line bit error rates.
Within the spectrum allocated to multi-channel multipoint distribution systems (MMDS), however, some spectrum is regulated for only FDD operation. Since the total spectrum allocated to MMDS is relatively small (2.5-2.7 GHz, or about 30 6 MHz channels), some service providers may desire to utilize the FDD-only spectrum, preferably utilizing the TDD-based equipment employed in other portions of the MMDS spectrum.
In one embodiment the present disclosure provides a method of TDD operation in a first subscriber unit having a cable modem. The method includes receiving in the first subscriber unit a first signal from a first base station on a downlink frequency during a first time period. The method includes transmitting from the first subscriber unit a second signal to the first base station on an uplink frequency during a second time period following the first time period. The downlink frequency and the uplink frequency are separated by a predefined duplex spacing.
In another embodiment, the present disclosure provides a cable modem configured to use TDD in a first subscriber station. The modem includes a receiver circuit to receive a first signal on a first frequency designated for downlink transmission during a first time period. The modem also includes a transmitter circuit to transmit a second signal on a second frequency different from the first frequency and designated for uplink transmission during a second time period following the first time period. The first frequency is employed for downlink transmission to a second subscriber station during the second time period and the second frequency is employed for uplink transmission from the second subscriber station during the first time period.
In still another embodiment, the present disclosure provides a method of time sharing frequencies reserved for FDD operation for use in conjunction with a cable modem. The method includes receiving in the cable modem a first signal from a first base station on a downlink frequency during a first time period. The method also includes transmitting from the cable modem a second signal to the first base station on an uplink frequency during a second time period following the first time period, wherein the downlink frequency and the uplink frequency are separated by a predefined duplex spacing.
In a further embodiment, the present disclosure provides a cable modem configured to use TDD. The cable modem includes a transmitter circuit configured to transmit a first signal on a first frequency to a first subscriber station during a first time period and transmit a second signal on a second frequency, different from the first frequency, to a second subscriber station during a second time period following the first time period. The cable modem also includes a receiver circuit configured to receive a third signal on the second frequency from the second subscriber station during the first time period and receive a fourth signal on the first frequency from the first subscriber during the second time period.
FIG. 1 illustrates exemplary wireless access network 100 according to one embodiment of the present disclosure;
FIGS. 2A-2B depict cell and sector layouts for a wireless access coverage area according to various embodiments of the present disclosure;
FIGS. 3A-3E are comparative high level timing diagrams illustrating the bandwidth allocation among sectors and cells according to the prior art and according to one embodiment of the present disclosure;
FIG. 4 depicts in greater detail a frame structure employed within the exemplary bandwidth allocation scheme according to one embodiment of the present disclosure;
FIG. 5 is functional diagram of filtering employed for wireless communication within each cell and sector in accordance with one embodiment of the present disclosure;
FIG. 6 illustrates a spectral response for filtering employed for wireless communication within each cell and sector in accordance with one embodiment of the present disclosure; and
FIG. 7 is functional diagram of filtering employed for wireless communication within each cell and sector in accordance with another embodiment of the present disclosure.
FIGS. 1 through 7, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless access network or in time division duplex (TDD) wireline applications such as, for example, cable modems.
FIG. 1 illustrates an exemplary fixed wireless access network 100 according to one embodiment of the present disclosure. Fixed wireless network 100 comprises a plurality of transceiver base stations, including exemplary transceiver base station 110, that transmit forward channel (i.e., downstream) broadband signals to a plurality of subscriber premises, including exemplary subscriber premises 121, 122 and 123, and receive reverse channel (i.e., upstream) broadband signals from the plurality of subscriber premises. Subscriber premises 121-123 transmit and receive via fixed, externally-mounted antennas 131-133, respectively. Subscriber premises 121-123 may comprise many different types of residential and commercial buildings, including single family homes, multi-tenant offices, small business enterprises (SBE), medium business enterprises (MBE), and so-called “SOHO” (small office/home office) premises.
It should be noted that network 100 was chosen as a fixed wireless network only for the purposes of simplicity and clarity in explaining a subscriber integrated access device according to the principles of the present disclosure. The choice of a fixed wireless network should not be construed in any manner that limits the scope of the present disclosure in any way. As will be explained below in greater detail, in alternate embodiments of the present disclosure, a subscriber integrated access device according to the principles of the present disclosure may be implemented in other types of broadband access systems, including wireline systems (i.e., digital subscriber line (DSL), cable modem, fiber optic, and the like) in which a wireline connected to the subscriber integrated access device carries forward and reverse channel signals.
FIG. 2A depicts a cell and sector layout for a wireless access coverage area according to one embodiment of the present disclosure. Coverage area 200 is logically divided into cells 210, 220, 230 and 240 each logically divided into a number of sectors 211-216, 221-226, 231-236 and 241-246, respectively. Each cell 210, 220, 230 and 240 includes a transceiver base station 110 as depicted in FIG. 1 at a central location 217, 227, 237, and 247, respectively, as well as subscriber premises 121-123 within the coverage area of the respective cell.
FIGS. 3C through 3E are high level timing diagrams illustrating bandwidth allocation among sectors according to one embodiment of the present disclosure, and are intended to be read in conjunction with FIG. 2A. The present disclosure incorporates FDD operation, with dedicated downlink and uplink channels, within a TDD system by introducing a frequency change at the normal. TDD guard point. Transmission time on the dedicated downlink frequency F1 and the dedicated uplink frequency F2 are divided between adjacent sectors within Categories A and B. Thus, the TDD FDD system 320 of the present disclosure allocates both a downlink period 321, 322 on the downlink frequency F1 and an uplink period 323, 324 on the uplink frequency F2 to each of the sectors within categories A and B.
FIG. 4 depicts in greater detail a frame structure employed within the exemplary bandwidth allocation scheme according to one embodiment of the present disclosure, and is intended to be read in conjunction with FIGS. 2 and 3C through 3E. The frame 400 depicted corresponds to each of the sectors within category A described above and depicted in FIGS. 2A and 3C through 3E, although each sector within category would utilize a similar frame, as described in further detail below.
Frame 400 includes a frame header 410, a downlink sub-frame 420, and an uplink sub-frame 430, with the downlink and uplink sub-frames logically divided into a number of physical slots 440. The frame header 410 includes a preamble 411 containing a start-of-frame field, which allows subscribers using fixed diversity to test reception conditions of the two diversity antennas, and a physical layer (the air interface is layered as a physical layer and a media access layer) media dependent convergence field, utilized to assist in synchronization and time/frequency recovery at the receiver. The preamble 411 is followed by media access management information 412, which includes a downlink MAP identifying the physical slot where the downlink ends and the uplink begins, an uplink MAP indicating uplink subscriber access grants and the associated physical slot start of the grant, and other management messages such as acknowledge (ACK) response, etc.
Frames for sectors falling within category B will have a similar structure, but will be offset so that the downlink sub-frame of each category B sector corresponds in time with the uplink sub-frame of each category A sector, and the uplink sub-frame of each category B sector corresponds in time with the downlink sub-frame of each category A sector. The boundary between downlink and uplink sub-frames is adaptive utilizing block equalization and burst timing coordination. Accordingly, uplink and downlink allocations to sectors in categories A and B may be divided equally as shown in FIG. 3C. or may be split to allow greater time within a particular frame to the downlink for sectors in category A, as shown in FIG. 3D, or to the downlink for sectors in category B, as shown in FIG. 3E. Spectral efficiency is therefore improved by adapting to the instantaneous traffic requirements among various sectors.
While the exemplary embodiment is described above with six sector cells and only two sector categories for the purposes of simplicity and clarity in describing the disclosure, the present disclosure may be extended to any number of sector categories equal to a power of 2 (e.g., 2, 4, 8, . . . , etc.), and preferably employs four sector categories. Where more than two sector categories are employed, downlink and uplink frequencies may be reused in pairs or in staggered offsets (e.g., each sector A shares a downlink frequency F1 with one adjacent sector B but shares an uplink frequency F2 with a different adjacent sector C, etc.). FIG. 2B depicts a cell and sector layout for a wireless access coverage area according to an alternative embodiment of the present disclosure. Coverage area 250 is logically divided into cells 260, 270, 280 and 290 each logically divided into four sectors 261-264, 271-274, 281-284 and 291-294, respectively. Each cell 260, 270, 280 and 290 includes a transceiver base station 110 as depicted in 28 FIG. 1 at a central location 265, 275, 285, and 295, as well as subscriber premises 121-123 within the coverage area of the respective cell.
FIG. 5 is functional diagram of filtering employed for wireless communication within each cell in accordance with one embodiment of the present disclosure, and is intended to be read in conjunction with FIGS. 1, 2A-2B, 3C-3E, and 4. The filtering system 500 depicted is implemented within each transceiver base station 110 and each subscriber access device on subscriber premises 121-123. The parameters for filtering system 500 implemented within each subscriber premises 121-123 will be described, although those skilled in the art will recognize that the filtering systems within each transceiver base station 110 will simply have the transmission and reception frequencies downlink or uplink frequencies F1 and F2) reversed or otherwise changed.
Wireless signals at the appropriate downlink and uplink frequencies F1 and F2 for the subject cell and sector are transmitted and received via antenna 501 and separated by a diplexer 502. Signals received from or passed to diplexer 502 are filtered utilizing filters 503 and 504 tuned to downlink and uplink frequencies F1 and F2, respectively. The signal received from filter 503 is mixed with a signal from a local oscillator 505 tuned to the downlink frequency F1 f while the signal transmitted to filter 504 is mixed with a signal from a local oscillator 506 tuned to the uplink frequency F2. If direct conversion is utilized, the output of mixer 507 may be connected directly to analog-to-digital (A/D) converter 508, and the input to mixer 509 may be connected directly to digital-to-analog (D/A) convert 510.
If super heterodyne conversion is employed, as is preferable, filtering system 500 includes a second (optional) conversion stage 511. Within conversion stage 5111 the output of mixer 507 passes to a filter 512 tuned to an image frequency based on the downlink frequency F1, with the filtered output being mixed with a signal from a local oscillator 513 also tuned to the image frequency based on downlink frequency F1 before being passed to A/D converter 508. Similarly, signals from D/A converter 510 are mixed with a signal from a local oscillator 514 tuned to an image frequency based on the uplink frequency F2 and is passed through a filter 515 also tuned to the image frequency based on the uplink frequency F2 before being passed to mixer 509.
Filtering system 500 should have two essential characteristics for successful implementation of a TDD FDD system in accordance with one embodiment of the present disclosure. First, the frequency switching time between the uplink and downlink frequencies for the filtering system 500 within all transceivers (within each transceiver base station 110 and each subscriber premises 121-123) must be sufficiently fast to complete during the frequency change physical slots 421 and 431. Frequency change physical slots 421 and 431, together with guard times 422 and 432, insure that transmission of an uplink/downlink sub-frame is completed successfully before transmission of the next sub-frame is started. Frequency switching should preferably take no longer than ¼ to 1/10 the duration of physical slots 421 and 431. Physical slots 421 and 431 and/or guard times 422 and 432 may alternatively be extended in duration to accommodate longer frequency switching times within a transceiver between the downlink and uplink frequencies.
Second, filtering system 500 must filter transmitted and received signals in depth to ensure, in conjunction with the duplex spacing employed between the downlink and uplink frequencies F1 and F2, that spurious out-of-band transmission products do not interfere with the receiver. FIG. 6 illustrates a spectral response for filtering employed for wireless communication within each cell and sector in accordance with one embodiment of the present disclosure. A signal strength 600 at which unacceptable interference prevents successful communication may be identified or defined for a particular system. Filtering system 500 should pass signals within the band 601 allocated to downlink frequency F1 and within the band 602 allocated to uplink frequency F2. By virtue of duplex spacing 313 between the downlink and uplink frequencies F1 and F2, together with the in-depth filtering performed by filtering system 500, out-of-band signals are sufficiently rejected to prevent the signal strength from approaching interference level 600.
FIG. 7 is functional diagram of filtering employed for wireless communication within each cell and sector in accordance with another embodiment of the present disclosure. Filtering system 700 receives wireless signals at the appropriate downlink and uplink frequencies F1 and F2 for the subject cell and sector via antenna 501. Signals received from or passed to antenna 501 are filtered utilizing filter 701, which covers the full FDD band employed for the subject sector. A switch 702 selective connects the filter 701 to a power amplifier (PA) 703 for transmission or to a low noise amplifier (LNA) 704 for reception.
The FDD TDD strategy of the present disclosure permits filtering and conversion to be performed along a single, bidirectional signal path which is reused for both the downlink and the uplink, eliminating the need for separate paths and reducing the system costs. The spectral performance illustrated in FIG. 6 should be implemented by filtering system 700, with the frequency switching time for local oscillator 705 within the first conversion stage being critical to meeting the timing requirements imposed by the FDD TDD system of the present disclosure.
1. A cable modem configured to use time division duplex (TDD) in a first subscriber station, the cable modem comprising:
a receiver circuit configured to receive a first signal on a first frequency designated for downlink transmission during a first time period; and
a transmitter circuit configured to transmit a second signal on a second frequency different from the first frequency and designated for uplink transmission during a second time period following the first time period,
wherein the first frequency is employed for downlink transmission to a second subscriber station during the second time period and the second frequency is employed for uplink transmission from the second subscriber station during the first time period.
2. A method of using time division duplex (TDD), comprising:
receiving a first signal on a first frequency designated for downlink transmission during a first time period using a receiver of a device; and
transmitting a second signal on a second frequency different from the first frequency and designated for uplink transmission during a second time period following the first time period using a transmitter of the device;
US13/532,650 2001-01-19 2012-06-25 TDD FDD communication interface Active US10264562B2 (en)
US11/982,404 US20080261588A1 (en) 2001-01-19 2007-10-31 TDD FDD communication interface
US13/532,650 US10264562B2 (en) 2001-01-19 2012-06-25 TDD FDD communication interface
US11/982,404 Continuation US20080261588A1 (en) 2001-01-19 2007-10-31 TDD FDD communication interface
US16/384,756 Continuation US20200015201A1 (en) 2019-04-15 Tdd fdd communication interface
US20120263079A1 US20120263079A1 (en) 2012-10-18
US10264562B2 true US10264562B2 (en) 2019-04-16
US09/839,499 Active 2023-07-01 US7346347B2 (en) 2001-01-19 2001-04-20 Apparatus, and an associated method, for providing WLAN service in a fixed wireless access communication system
US11/982,459 Abandoned US20080259826A1 (en) 2001-01-19 2007-10-31 System for coordination of communication within and between cells in a wireless access system and method of operation
US11/982,463 Abandoned US20080259868A1 (en) 2001-01-19 2007-10-31 Wireless communication system and associated method for routing messages to wireless networks
US11/982,461 Abandoned US20080254801A1 (en) 2001-01-19 2007-10-31 Method and apparatus for establishing a priority call in a fixed wireless access communication system
US11/982,424 Abandoned US20080268835A1 (en) 2001-01-19 2007-10-31 Wireless communication system and device for coupling a base station and mobile stations
US11/982,404 Abandoned US20080261588A1 (en) 2001-01-19 2007-10-31 TDD FDD communication interface
US13/488,374 Active 2021-06-23 US9426794B2 (en) 2000-11-15 2012-06-04 Wireless communication system and device for coupling a base station and mobile stations
US13/532,650 Active US10264562B2 (en) 2001-01-19 2012-06-25 TDD FDD communication interface
US20150171512A1 (en) * 2013-12-17 2015-06-18 Elwha Llc Sub-nyquist holographic aperture antenna configured to define selectable, arbitrary complex electromagnetic fields
2001-04-20 US US09/839,499 patent/US7346347B2/en active Active
2007-10-31 US US11/982,459 patent/US20080259826A1/en not_active Abandoned
2007-10-31 US US11/982,463 patent/US20080259868A1/en not_active Abandoned
2007-10-31 US US11/982,461 patent/US20080254801A1/en not_active Abandoned
2007-10-31 US US11/982,424 patent/US20080268835A1/en not_active Abandoned
2007-10-31 US US11/982,404 patent/US20080261588A1/en not_active Abandoned
2012-06-04 US US13/488,374 patent/US9426794B2/en active Active
2012-06-25 US US13/532,650 patent/US10264562B2/en active Active
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