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MXPA00004508A - Frequency-time division duplex in radio communications systems - Google Patents

Frequency-time division duplex in radio communications systems

Info

Publication number
MXPA00004508A
MXPA00004508A MXPA/A/2000/004508A MXPA00004508A MXPA00004508A MX PA00004508 A MXPA00004508 A MX PA00004508A MX PA00004508 A MXPA00004508 A MX PA00004508A MX PA00004508 A MXPA00004508 A MX PA00004508A
Authority
MX
Mexico
Prior art keywords
base station
time
frame
communications
time slots
Prior art date
Application number
MXPA/A/2000/004508A
Other languages
Spanish (es)
Inventor
Lenzo Michael
Shen Qun
Original Assignee
Ericsson Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ericsson Inc filed Critical Ericsson Inc
Publication of MXPA00004508A publication Critical patent/MXPA00004508A/en

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Abstract

A flexible channel architecture supports full-duplex, radio-frequency communication between a base station, such as a PWT or DECT base station, and a group of remote terminals. Communication from the base to the terminals is by way of a radio-frequency carrier having a first frequency, and communication from the terminals to the base is by way of a second radio-frequency carrier having a second frequency. Each carrier is organized to provide an N-timeslot time-division multiple access data stream (N an integer), so that together the two carriers provide a 2N-timeslot system. Within each data frame, data from the base to the terminals is sent on the first carrier during a first half of the frame, and data from the terminals to the base is sent on the second carrier during the remaining half of the frame. An additional, complementary base station, constructed to transmit when the first base station is receiving and vice versa, can be co-located with the first base station to provide full time and spectral efficiency within a coverage area serviced by the base stations.

Description

DUPLEX OF FREQUENCY-TIME DIVISION? N RADIO COMMUNICATIONS SYSTEMS Field of the Invention The present invention relates to radio communication systems, and more particularly to double schemes in multiple access time division (TDMA) systems.
BACKGROUND OF THE INVENTION Most multiple access time division wireless communications systems employ either a double time division scheme (TDD) or a double frequency division scheme (KDD) to separate uplink transmissions and downlink. Posts that both double schemes provide certain advantages and disadvantages, both schemes are routinely used in wireless communications applications. For example, in the Personal Wireless Telecommunication (PWT) standard, time division multiplex access with time division duplex is used to plan in frequency as well as signal packet and time slot allocation. Such a double time division / time division multiple access scheme is well suited for many business wireless communication applications (eg, small field systems, with micro or peak cells). On the other hand, multiple division time access with time division duplex or duplex frequency division r may be preferably for frequency bands of Licensed Personnel Communication Service (PCS), depending on the client's demands and market requirements, In other words, since the structure of a Personnel Communications Service system is determined primarily by a service provider that has acquired a portion of the frequency spectrum, technology and frequency usage implemented in This system is ultimately driven by customer demand - as well as legal and regulatory restrictions. practices. While a first client may require a time division / time division multiple access duplex system for a particular business wireless application, a second client may subsequently demand a dual time vision / frequency division multiple access system. for a wireless local circuit application. In this way, product and service providers are often required to convert between double schemes, converting between double schemes, however, it typically results in duplicate effort and, therefore, wastes significant time and resources. For example, since the conventional time division duplex and the double frequency division schemes are fundamentally different, it is generally not feasible to use a common hardware platform for both types of systems. As a result, two development groups are typically assigned, and two separate product lines are usually established, to provide both time division duplex and frequency division duplex implementations. Thus, there is a need for a flexible double scheme that allows a communications system to be adapted to satisfy varying customer needs without requiring modification of the basic system hardware architecture.
SUMMARY OF THE INVENTION The present invention fills the needs described above and others by providing a flexible double division mechanism in a time division multiple access communications system. More specifically, the described system uses a double division, hybrid or mixed mechanism, so that the uplink and downlink transmissions are frequency separated while the time slots associated with transmission and reception are also separated in time. . The hybrid double scheme, hereinafter referred to as duplex, "frequency-time division (FTDD), allows r alternative double division mechanisms to be selectively implemented within a communications system without requiring modification of the basic hardware architecture of the system., the system described can use a single hardware platform for applications where either the time division duplex or the frequency division duplex is preferred. In accordance with example modalities, the described system r is not a double system pure time vision, in which the same frequency band is used for both uplink and downlink transmissions, nor a dual pure frequency division system in which both uplink and downlink transmissions occur simultaneously. Rather, the described system uses separate frequency bands as well as separate time slots for uplink and downlink communications. In this way, a hardware platform is initially designed for use in a dual time division / time division multiple access system can be easily adapted for use in a dual time division / frequency division multiple access system, and více versa, without significant modification of the hardware. This feature of the present invention results in lower non-recurring engineering costs and shorter system development time. Additionally, since the uplink and downlink communications are separated in both frequency and time, the described system provides less cross-channel interference compared to the prior art systems. Also, since a single hardware path can be used for both uplink and downlink transmissions in both base stations and terminals, the embodiments of the present invention retain the low cost and power consumption advantages typically associated with dual systems. of conventional time division. The present invention also provides methods and apparatus that allow a frequency-time division system to operate without loss of spectral efficiency. In accordance with an exemplary embodiment, a wireless communication system 'includes a plurality of mobile stations and a base station. The base station is configured to transmit downlink communications signals to the mobile stations through a first carrier frequency and to receive signals of up / down communications from the mobile stations through a second carrier frequency, the signals from downlink and uplink communications being transmitted and received through. of successive time division multiple access frames, each frame including a plurality of time slots. For each active communication link (eg, for each call) established between the base station and a mobile station, a first time slot within each frame is allocated for downlink communications and a second time slot within each frame is intended for uplink communications, the first and second time slots distributed being separated in time by a fixed time deviation, In accordance with the modality, a first division of the time slots within each frame it is reserved for downlink communications from the base station to the mobile stations and a second division of the time slots within each frame is reserved for uplink communications from the mobile stations to the base station, the communications system it may also include an additional base station placed with the first base station and configured as a man it was similar to transmit downlink communications signals to the mobile stations through the first carrier frequency and receive uplink communication signals from the mobile stations through the second carrier frequency, the downlink and link communications signals. ascending of each of the additional base stations being transmitted and received through successive multiple access frames "of division, of time, each frame including a plurality of time slots. For each active communication link established between the additional base station and a mobile station, a first time slot within, - of each frame of the additional base station is intended for downlink communications from the additional base station and a second time slot within each frame of the additional base station - is intended for uplink communications to the additional base station, the first and second distributed time slots being separated in time by a fixed time offset. A first division of the time slots within each frame of the additional base station is reserved for uplink communications and a second division of the time slots within each frame of the additional base station is reserved for link communications falling. For proportional full time and spectral efficiency for the coverage area served by the two base stations placed, the first and second divisions of the frames of each of the base stations are structured so that, for each time slot in each frame, only one of the base stations is allowed to transmit on the first carrier frequency and only one of the base stations is allowed to receive on the second carrier frequency, the features described above and others of the present invention they are explained in detail- below with reference to the illustrative examples shown in the accompanying drawings. Those skilled in the art will note that the described modalities are provided for purposes of illustration and understanding and that numerous modalities are contemplated herein. equivalents BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an exemplary wireless communications system in which the teachings of the invention can be implemented. Figure 2A illustrates a base station and a terminal communicating in accordance with a conventional time division / time division multiple access double scheme. Figure 2B illustrates an exemplary time slot arrangement in a conventional time division / time division multiple access dual system, Figure 3A illustrates a base station and a terminal communicating in accordance with a standard system. multiple time division / conventional frequency division access. Figure 3B is an exemplary time slot arrangement in a conventional double frequency division / time division multiple access system. Figure 4A illustrates a base station and a terminal communicating in accordance with a double scheme. multiple time division / frequency-time division access taught by the present invention. - Figure 4B illustrates an exemplary time slot arrangement in a double time division / frequency division time multiple access system according to the invention. Figure 4C illustrates an alternative and complementary time slot arrangement in a time division / division, multiple access system of frequency-time according to the invention. Figure 5 illustrates the reference time between two groups of base stations in an example multiple division access system. of time / frequency-time division according to the invention. Figure 6 illustrates an exemplary base station transceiver constructed in accordance with the present invention.
Detailed Description of the Invention Figure 1 illustrates a wireless communication system 100 in which the teachings of the present invention can be implemented. As shown, the exemplary wireless system includes ten cells or cover areas C1-C10, ten base stations B1-B10, one timer master TM and ten mobile stations M1-M10.This wireless system can be constructed, for example , in accordance with the Personal Wireless Telecommunication (PWT) standard, and can therefore be used, for example, for proportions of mobile communications within a building or through a campus that includes many buildings and open areas. A wireless system can include much more than ten cells, ten base stations and ten mobile stations, however, ten of each is sufficient for illustrative purposes, as shown, one or more base stations can be located in each of The cells, even though, Figure 1 shows the base stations placed towards the cell centers, each base station can instead be placed anywhere within a cell. Cell, base stations placed towards the center of the cell typically employ omnidirectional antennas, while base stations placed toward a cell boundary typically employ directional antennas. The timing master TM, or radio exchange, maintains synchronization-timing between the base stations as is known in the art. The timing master can be connected to the base stations by cable, radio links, or both. Each base station and each mobile station includes a transceiver to transmit and receive communication signals through the air interface. Typically, the base and mobile stations communicate using a time division, frequency division or code multiple access (i.e., TDMA, FDMA or CDMA) as is known in the art. As mobile stations move within a cell and * from cell to cell, communication with at least one base station is always possible. As a result, mobile station users are able to place, receive and conduct calls anywhere within the total coverage area of the system. To illuminate the particulars and advantages of the hybrid frequency-time division (FTDD) scheme of the present invention, time division-double (TDD) and conventional division-frequency (FDD) doubles are described below with with respect to Figures 2A, 2B, 3A, and 3B. Without loss of generality, the channel definition in the Personal Wireless Telecommunication Standard is used to illustrate a conventional time division multiple access (TDMA) / TDD system. Even though the channel definitions may differ between standards, the multiplexing and duplicate base concepts remain the same. Figure 2A illustrates uplink and downlink communication in accordance with a conventional TDD scheme. As shown, the signals transmitted from a TDD base station B20 to a TDD M20 device, and those 'transmitted from the TDD telephone M20 to the TDD base station B20, are separated in time. If, as shown in Figure 2B, 'a predetermined time interval T represents the duration of a single T20 TDMA / TDD frame, then the separation between uplink and downlink transmissions is typically half of. a predetermined time interval T, or T / 2. In a Personal Wireless Telecom system, each frame is 10 milliseconds in length and includes twenty-four data slots. Within a data frame, twelve time slots are used for transmission (from the TDD base station B20 to the TDD M20 telephone), and the remaining twelve time slots are used for reception (ie, transmission). from TDD M20 telephone to station B20-TDD base station). Even when transmissions and receptions are separated by a certain fixed (or variable) time, they share a common frequency band. 1 channel of said system, therefore, is defined by a predetermined frequency and frequency reference pair. Such TDMA / TDD systems are widely adopted in various applications of wireless communications.One advantage of these systems is that of frequency efficiency, since both uplink and downlink transmissions use a common frequency carrier, in addition, since that transmissions and receptions are separated, 'in time, a single hardware path (including filters, local oscillators, etc.) can be used for both functions.As a result, TDD systems are relatively inexpensive. .the reception hardware can be disconnected during transmission (and the transmission hardware can be disconnected during reception), the TDD systems consume relatively little energy.By contrast, frequency division duplex (.FDD) systems require bands of separate frequency for uplink and downlink communications. of the fact that the reception and transmission operations - are executed simultaneously in time at different frequencies, A channel in an FDD system is thus defined by the frequency of operation. Figure 3A illustrates uplink and downlink communications between a conventional FDD base station B30 and a conventional FDD telephone M30, and Figure 3B shows an example TDMA / FDD frame T30.
Since both transmission and reception are achieved simultaneously, separate hardware paths are required at "both base stations and terminals." As a result, FDD systems are typically higher cost and consume more power compared to conventional TDD systems, However, FDD systems provide relatively little cross-channel interference and are sometimes preferred from an inter-system perspective: in other words, an FDD scheme may be required to make a system compatible with nearby systems using an adjacent portion of the spectrum As a result, FDD systems have also been widely adopted in wireless communications applications.While both TDD and FDD r systems provide certain advantages, none are ideally suited for all wireless communications applications. described above, the differences fund Actors between TDD and FDD make it difficult to adapt a system configured specifically for one or the other to conform to a particular application need. Advantageously, the present invention provides a hybrid frequency-time division (FTDD) duplex scheme, which provides certain of the advantages of both types of conventional system and which also allows a single hardware configuration to be easily adapted to be appropriate. virtually any wireless communications application, Figure 4A illustrates a FTDD base station B40 and an MT telephone of FTDD that communicates in accordance with the TDMA / FTDD scheme of the present invention. As shown, the signals transmitted from base station B40 from FTDD to telephone M40 from FTDD, and those transmitted from telephone M40 TDD to base station B40 from FTDD, are separated in both time and frequency. A definition of, general channel for that TDMA / FTDD scheme is described in the Request for Patent of E.U.A. Copendi ate Serial No., entitled "Frequency Division Duplex-Flexible Time in Radio Communication Systems" and I filed on the same date as the present one, which is hereby incorporated by reference in its entirety. While the general channel definition provides a large degree of flexibility, the present invention teaches that certain advantages in terms of complexity - reduced hardware and total reduced software can be achieved by reducing some flexibility. Specifically, the present invention teaches that certain advantages can be derived by dividing a TDMA / FTDD frame and reserving certain time slots for either "uplink or downlink transmission." Two example channel definitions T40a, T40b according to the scheme of the present invention are illustrated in Figures 4B and 4C, respectively Without losing the generality, a data box for the channel definitions of Figures 4B and 4C is defined r which includes 2N time slots (N an integer.) Half of the slots (ie, a first N slots) are reserved for transmission from a base station to a portable one, and the remaining half of the slots - (ie, a second N slots) are reserved. are reserved for transmission from a portable station to a base station Assuming that the time durations of downlink and uplink slots are provided by d and u, respectively, then the duration T of - a single frame in the frequency-time division duplex scheme is provided by T = N (d + u), In accordance with channel definition T40a of Figure 4B, a higher frequency band - is reserved for base station to telephone transmission, and a lower frequency is reserved for telephone transmission to base station In this way, the first N time slots in one frame are dedicated for F downlink communication, and the second N slot Time is allocated for uplink communication. Inverse, in accordance with the alternative and complementary channel definition of "Figure 4C, the second N time slots are reserved for downlink communication, and the first N time slots are reserved for uplink communication. that the transmission and reception time slots are of the same duration (ie, d = u), half of the T-box, or T / 2, reserved for downlink signals and the remaining half is reserved for signals of Uplink - Placing - a first base station that operates in accordance with the channel definition of the .. Figure 4B with a second base station operating in accordance with the channel definition of Figure 4C, full time and efficiency can be provided for a particular coverage area In other words, both frequencies in each TDMA time slot can be used for uplink or downlink transmission. To ensure that a complete system constructed in accordance with the invention operates in an appropriate manner, the timing alignment between base stations is maintained. Specifically, the individual base stations move in time with respect to a base reference. For example, a first group of base stations can employ zero deviation so that they operate in accordance with the channel definition of Figure 4B, and another group of base stations can employ a half-square deviation (i.e. , T / 2) so that they operate in accordance with the channel definition of. Figure 4C, In this way, the uplink and downlink transmissions for the second group of base stations are deviated by T / 2 with respect to those of the base stations in the first group, by combining a or more base stations of each group in common locations (e.g., in each cell in a wireless coverage area), a system in accordance with the invention can achieve frequency and time efficiency while maintaining full capacity for radio stations. individual bases. The chronometration relationship described above between base stations is illustrated in Figure 5. As shown, two reference momentum start clocks are deviated by T / 2. A first group of base stations B40a are connected to the base reference clock (zero deviation), while a second group of base stations B40b are connected to the offset reference (1/2 deviation). An additional deviation is maintained at the network level to keep the individual calls aligned, Do this way, during the FTDD operation (ie, when 'separate uplink and downlink frequencies are used), the first group of stations Base B40a operates in accordance with the channel definition of Figure 4B, while the second group of base stations B40b operates in accordance with the channel definition of Figure 4C, Note that using a standard reference deviation box is maintained synchronization, slot between base stations, making it possible. ' synchronized communication with telephones for both groups of base stations The resulting system thus maintains the capacity of individual base stations when operating in a duplex-time-division mode, while allowing base stations to be placed recover full time and spectral efficiency when operating in a frequency-time division duplex mode.Thus, with proper base station synchronization, it is possible for a telephone to conduct communication with any base station in a complete system. Specifically, telephones need only adhere to the rule that time slots are paired with "half-frame separation between uplink and downlink transmissions while independently maintaining simultaneous communications to both types of base station. In this way, seamless transfers between all base stations can be achieved in a complete system. Those experiments in the art will note that the timing described above can be achieved through direct software modification of existing systems. Those skilled in the art will also appreciate that a system employing two groups <; of base stations with half frame deflection between groups is only one example embodiment of the present invention. Generally, any number of base station groups can be used with fixed time slot deviations between the groups. For example, four groups of base stations can be implemented using frame quarter deviations between groups. In such a case, each group reserves a quarter of the time slots in each TDMA frame for uplink transmission and another quarter of the slots of time in each TDMA frame for downlink transmission, frames are reserved for each group so that, at any moment in time, at most a group of base stations can transmit on the downlink frequency and at most a group of base stations can receive on the uplink frequency. In this way, x four co-located base stations, one from each of the four groups, can provide full time and spectral efficiency for a particular coverage area. Note that the time slots reserved for uplink and downlink transmission for a particular type of base station they do not need to be consecutive time slots within a TDMA frame. for example, in a two-group system such as that illustrated in Figures 4B, 4C and 5, the first group of base stations can reserve even-numbered time slots for downlink communication and odd-numbered time slots. for uplink communication, while the second complementary group of base stations reserves odd downlink communication time slots and even number time slots for uplink communications Those skilled in the art will immediately appreciate that every possible combination of Additional time slot arrangement is contemplated herein. It is only important that, once a particular division of time slots is reserved for uplink or downlink transmission by a group of base stations, the time slots x in this particular division can not be used for the same. type of transmission by ~ another group of base stations. In fact, the time slots reserved for uplink or downlink transmission for each base station group can be randomly distributed across the TDMA frames. As noted above, since the uplink and downstream transmissions occur at separate times, a system using the FTDD scheme of the present invention can be constructed so as to transmit and receive paths in both, a base station and a terminal are shared as in a conventional time division duplex system. As a result, a system constructed in accordance with the invention provides the advantages of relatively low cost and low energy consumption. This aspect of the invention is illustrated in Figure 6,, In Figure 6, an exemplary base station transceiver 600 includes a signal processing path of "transmission and a reception signal processing path, as shown. , the transmission processing path includes first and second transmission blocks 610, 620, first and second transmission / reception blocks 630, 640 ', a local oscillator 650, a duplicator 660 and an antenna 670. Additionally,. reception signal processing includes local oscillator 650, duplicator 660 and antenna 670, as well as first and second reception blocks 680, 690. First transmission block 610 may include, for example, a conventional upconverter, and the second transmission block 620 may include, for example, power amplifiers and mixers., the first reception block 680 may include, for example, low noise amplifiers (LNA) and mixers, and the second reception block 690 may include, for example, a conventional downconverter and limiter. The first transmit / receive block 630 may include, for example, a modem, and the second transmit / receive block 640 may include, for example, bandpass filters. The duplicator 660 can be, for example, a two-step filter or a switch. During the downlink transmission, the duplicator 660 couples the antenna 670 to the second transmission block 620 and isolates the antenna 670 from the first reception block 680. The baseband x transmit signals are processed by the first transmit / receive block 630 and then up-converted, filtered and amplified in blocks 610, 640, 620, respectively, before transmission through the antenna 670. Conversely, during uplink reception, the duplicator 660 couples the antenna 670 to the first reception block 680 and isolates the antenna 670 from the second transmission block 620, the radio frequency signals are received at the antenna 670 and they are then amplified, filtered and converted downwards into blocks 680, 640 and 690, respectively, before being processed by the first transmission / reception block 630, because the transmission and reception processing paths share certain components (i.e. , those components in the first and second blocks 630, 640- transmission / reception, which are typically very expensive), a station transceiver The base constructed in accordance with the invention can be made smaller and less expensive compared to conventional TDMA / FDD transceivers, even though the described frequency-time division duplex scheme is not a true frequency division duplex system, in which transmission and reception are not conducted simultaneously, the duplex x-frequency division scheme however seems to close systems as a duplex scheme of frequency division from the perspective. of interference between systems. In this way, a system that uses the frequency-time division duplex scheme can be implemented in contexts where a split-frequency duplex scheme is preferred. Additionally, the hardware configured to implement the frequency-time division scheme can also be used when the time division duplex is preferred. In other words, a simple software change can be used to shift one or both of the uplink and downlink frequencies (i.e. by changing the frequencies of the local oscillators used to generate the corresponding carriers) so that the link frequencies Ascending and downlinking are the same time and the system operates as a true time division duplex system. In this manner, a time division multiple access system constructed in accordance with the present invention can easily be configured to use either a time division duplex scheme or a pseudo frequency division duplex scheme. Additionally, a system originally configured to use time division duplexes can easily be converted to use frequency division duplexes, and vice versa, as needs change. Selling these conversions can be achieved quickly and inexpensively without modifying the architecture. In sum, the present invention provides a time division multiple access system with a flexible frequency-time division duplex mechanism. In accordance with the invention, the time vision / time division multiple access multiple duplex hardware. can be used for applications where - the frequency division duplex is preferred or required. The system described allows either a common frequency band and double frequency bands to be used for uplink and downlink communications. Advantageously, the duplex capability of time division is maintained, as well as the benefits of low cost hardware and low power consumption, - A system can be converted repeatedly for F both, time division duplex and frequency division duplex without requiring significant hardware modification. Those skilled in the art will note that the present invention is not limited to the specific exemplary embodiments that have been described herein for purposes of illustration. The scope of the invention, therefore, is defined by the claims appended thereto. the present, in place of F by the foregoing description, and all equivalents which are consistent with the meaning of the claims intended, to be encompassed in -the same,

Claims (20)

1. - A base station for use in a wireless communication system that includes a plurality of mobile stations, the base station comprising: a transceiver configured to transmit downlink communications signals to mobile stations through a first carrier frequency and to receive communications signals. uplink of the mobile stations through a second carrier frequency, the signals of F downlink and uplink communications being transmitted and received through successive multi-access frames of division, time, each frame including a plurality of time slots, wherein for each active communication link between the base station and a particular mobile station, a first time slot in each frame is intended for "downlink" communication to the particular mobile station and a second slot of time in each frame is allocated for uplink communication from the particular mobile station, the first and second time slots distributed being separated in time by a fixed time offset, and wherein a first division of the time slots within the each frame is reserved for downlink communications from the base F station to the mobile stations and a second division of the time slots within each frame is reserved for uplink communications from the mobile stations to the base station.
2. A base station according to claim 1, wherein a first half of the time slots between each frame are reserved for downlink communications and a second half of the time slots within each frame are reserved for uplink communications.
3, - A base station according to claim 2, wherein,. within each frame, each of the reserved time slots for downlink communications is placed earlier in time with respect to each of the slots - of reserved time for uplink communications.
4. A ba & ß station in accordance with F claim 2, wherein, within each frame, each of the reserved time slots for downlink communications is placed later in time with respect to each of the time slots reserved for uplink communications.
5. A base station according to claim 2, wherein, within each frame, consecutive time slots are reserved alternately for downlink and uplink communications.
6. A base station according to claim 1, wherein, for N a positive integer and M a positive integer less than or equal to 2N, 2N being equally divisible among M, each frame includes 2N time slots, one first 2N / M of whose time slots are reserved for downward decoding communications and a second 2N / M whose time slots are reserved for uplink communications.
7. A base station according to claim 1, wherein a duration of the fixed time offset is the same for each active communication link.
8. A base station according to claim 7, wherein each frame is of a duration T and includes a number, 2N, of time slots, each timeslot being of a duration T / 2N, and where The duration of the fixed time deviation for each active communication link is T / 2.
9, - A base station according to claim 1, wherein a downlink signal processing path and a transceiver uplink signal processing path share common sr signal processing components.
10. A base station according to claim 9, wherein the shared signal processing components include at least one of a filter, a local oscillator and a modem,
11. A wireless communication system, comprising : • _ a plurality of mobile stations; and - t a first base station configured to transmit downlink communications signals to the mobile stations through a first carrier frequency and to receive signals - from uplink communications from the mobile stations through a second frequency carrier, the downlink and uplink communication signals being transmitted and received through successive multiple access frames -, time division, each frame including a plurality of time slots, - wherein for each active link of communications, between the first base station and a mobile station, a first time slot within each frame is intended for downlink communications and a second time slot within each frame is intended for uplink communications, the first and second time slots distributed being separated in time by a deviation n of fixed time, and wherein a first division of the time slots within each frame is reserved for downlink communications from the first base station to the mobile stations and a second division of the time slots within each frame it is reserved for uplink communications from the mobile stations to the first base station.
12. A communication system according to claim 11, wherein a first half of the time slots within each frame are reserved for downlink communications and a second half of the time slots within each frame are reserved. for uplink communications.
13. A communications system according to claim 11, wherein, for N a positive integer and M a positive integer less than or equal to 2N, 2N being equally divisible among M * each frame includes 2N time slots, a first 2N / M whose time slots are reserved for downlink communications and a second 2N / M whose time slots are reserved for uplink communications. F
14. A communication system according to claim 11, wherein one duration of the fixed time offset is the same for each active communication link.
15, - A communication system according to claim 14, wherein each frame is of a duration T and includes a number, 2N, < of time slots, each time slot being of duration T / 2N, and wherein the duration of the fixed time offset for each active communication link is T / 2.
16. A communication system according to claim 11, wherein a downlink signal processing path and an uplink signal processing path of the first base station share common signal processing components.
17. - A communication system according to claim 16, wherein the shared signal processing components include at least one of a filter, a local oscillator and a modem
18. A communication system, in accordance with claim 11, further comprising at least one additional base station co-located with the first base station and configured to transmit downlink communication signals to the mobile stations through the first carrier frequency and to receive communications signals from uplink from the mobile stations through the second carrier frequency, -the signals of downlink and uplink communications of each of the additional base stations being transmitted and received through successive multiple division access frames 'of time, each frame including a plurality of time slots, where pa Each active communication link between an additional base station and a -mobile station, a first time slot within each frame of the additional base station is intended for downlink communications from the additional base station and a second time slot within each frame of the additional base station is intended for uplink communications to the additional base station, the first and second distributed time slots being separated in time by a fixed time offset, wherein the first division of the x time slots within each frame of each additional base station is reserved for uplink communications and a second division of the time slots within each frame of each additional base station is reserved for downlink communications, and where the first and second divisions-of the tables of each of the base stations is structured so that, for each time slot in each frame, only one of the base stations is allowed to transmit on the first carrier frequency and only one of the base stations is allowed to receive on the second carrier frequency.
19. A communications system according to claim 18, wherein the first base station is co-located with a single additional base station, wherein first and second halves of the time slots of each frame of the first base station coincide in time with the first and second halves, respectively, of each frame of the single additional base station, wherein the "first and second halves of the time slots of each frame of the first base station are reserved, respectively, for downlink communications from the first base station and uplink communications to the base station, and wherein the first and second halves of the time slots of each frame of the single additional base station are reserved, respectively, for uplink communications to the single additional base station and downlink communications from the single station additional base
20. A method for conducting communications between base stations and mobile stations in a wireless communication system, comprising the steps of: co-locating at least two base stations; transmitting communication signals between the co-located base stations and the mobile stations using time-division multiple access frames, each frame including a plurality of time slots, wherein the signals of downlink communications from the stations base co-located to the mobile stations are transmitted through a first carrier frequency and the "uplink" communication signals from the mobile stations to the co-located base stations are transmitted through a second carrier frequency; and for each of the co-located base stations, reserve first and second divisions of time slots within each frame for downlink and uplink links, respectively, so that, at any time in time, at most one of the co-located base stations is transmitting through - the first carrier frequency and at most one of the co-located base stations is receiving through the second carrier frequency.
MXPA/A/2000/004508A 1997-11-14 2000-05-10 Frequency-time division duplex in radio communications systems MXPA00004508A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US60/065,799 1997-11-14

Publications (1)

Publication Number Publication Date
MXPA00004508A true MXPA00004508A (en) 2001-07-09

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