MXPA99007963A - Rangoextend concentral celda base station - Google Patents

Abstract

The present invention relates to a concentric cell base station d extended range and a method to extend a cell size or an access range without incurring ASIC correlator redesign. This is achieved with a concentric cell base station signal that incorporates multiple synchronization protocols and search windows. The concentric base station has associated a micro cell and a macro cell, where the micro and macro cells use the same frequency band but different synchronization protocols and search windows that will cause signals transmitted by mobile phones within their respective cells , are received within the confines of at least one search window

Description

CONCENTRIC CELL STATION * OF EXTENDED RANGE FIELD OF THE INVENTION The present invention relates generally to wireless communication systems and in particular to extending the access ranges of wireless communication systems. BACKGROUND OF THE INVENTION Figure 1 illustrates a wireless communication system 10, which employs multiple access techniques with code division (CDMA = Code Multiple Access Division) based on the well-known standard IS-95 of the Telecommunication Industrial Association (Association Telecommunications Industry). The wireless communication system 10 comprises a mobile switching center (MSC = Mobile Switching Center) 12 and a plurality of base stations (BS = Base Stations) 14-i connected to the MSC 12. Each of the BS 14-i provides wireless communications services to mobile telephones (MT = Mobile-Telephones), such as 16-k mobile telephones, within an area of associated geographic coverage, here referred to as cell 18-i, with a radio Rx. For illustrative purposes, cells 18-i are illustrated as circular in shape, with base stations 14-i centrally located. It will be understood that the cells REF .: 30736 18 -i. they can also be non-circular (for example hexagonal) with the base stations placed non-centrally, and that the "radius Ri" should be constructed to define a distance between the base station and a point on the circumference of cell 18- i. (which will vary depending on the particular point in the circumference). Each base station 14-i. it includes radios and antennas for modulating and transmitting base station signals to mobile telephones, and for receiving and demodulating signals from mobile telephones within its associated cell 18 -i. Each base station 14-i also includes a receiver for information of synchronization, using the well known global location satellites (hereinafter referred to as "GPS receivers", (GPS = Global Positioning Satellites)). The signals are transmitted by the base stations 14-i. and mobile phones according to a synchronization protocol aligned with GPS time using a GPS receiver. Figure 2 illustrates a synchronization program 20 incorporating an implementation of a synchronization protocol based on the IS-95 standard. The synchronization program 20 comprises a series of frames 22 -n, wherein each frame 22 -n extends over a time interval t. The start of each frame 22 -n is marked by a frame border a time Tn aligned to the GPS time. According to the synchronization protocol, the base stations 14-i are configured to begin transmitting the base station signals at the frame boundaries, where the signals from the base station include signals containing zero or more information and a Pilot signal for coherent demodulation of information containing signals by mobile phones and system access operations. In contrast, 16-k mobile phones are configured to begin transmitting signals from mobile telephones at some multiple x of a frame time period (i.e., Jtx) after the 16-k mobile phones began receiving the signals. base station signals, where x is some integer greater than or equal to zero. Unlike base stations, mobile telephone signals include one or more signals that contain information and do not contain a pilot signal, and are encoded using a set of orthogonal codes (referred to as Walsh codes) combined with a pseudo-interference sequence (PN = pseudo-noise) (or a known code) such that the signal containing information can be demodulated in a non-coherent manner. The PN sequence comprises random digital signals 0 and 1, wherein the duration for a 0 or 1 to transmit is referred to herein as a PN chip.

The synchronization protocol described above will now be discussed with reference to Figure 3, which illustrates a time diagram 28, which shows a sequence of transmissions and receptions by the base station 14-i and a 16-k mobile telephone. At the time Tl r BS 14-1 begins transmitting the signal from base station S to MT 16-k, so it can be located at any point in cell 18-i. MT 16-k begins to receive the Sx signal at time T1 + dBS? MT, where dBS-lMr is a propagation delay from BS 14-i to MT 16-k. It should be noted that the term propagation delay should be considered to include line of sight propagation delays and no line of sight. MT 16-k will wait for a time interval tx from the moment when MT 16-k will begin to receive the signal S before it starts to transmit the mobile phone signal S2. In this way, MT 16-k will start transmitting signal S2 to time T -? + Dn.g-.Mt + tx (or time dBS- >; MT after- some frame boundary). For example, if x = 2, then MT 16-k transmits signal S2 to time T3 + dBS_MT (or two frames after receiving the base station signal Sx). Due to a propagation delay dMT? BS_from MT 16-k to BS 14-i, BS 14-i will start to receive signal S2 at time T1 + dBS_MT + tx + dMT_BS. For ease of discussion it is considered that the propagation delay dMT_BS of MT 16-ka BS 14-i is the same as the propagation delay dBS_MT, and both will then be referred to individually as a one-way propagation delay dow, i.e. , dsw = d?, BS = dBS? MT, or collectively as a propagation delay of round trip 2dow. In this way, BS 14-i will begin to receive signal S2 at time T1 + tx + 2dow. In order to demodulate the received signal S2, BS 14-i must first detect the signal S2. Each radio includes a correlator, which is a device that detects mobile phone signals. For example, the correlator detects the mobile phone signal S2 by multiplying an input signal by the PN sequence, wherein the PN sequence is shifted in time in discrete steps during a period or time interval (referred to here as a search window). Wn,) until the resulting product (of the PN sequence and the input signal) exceeds until it indicates the detection of the S2 mobile telephone signal. If BS 14-i does not begin to receive the signal S2 within the confines of the search window Wn BS 14-i it will not be able to detect the signal S2 (using the synchronization protocol incorporated in Figure 2). To ensure that BS 14-i begins receiving the signal S2 within the confines of the search windows Wn, the search windows Wn should extend time intervals that include possible arrival times for the signal S2 (traveling a line path straight line or line of sight between the mobile phone and the base station) regardless of the position of the 16-k mobile phone in cell 18-i. Based on the synchronization protocol described above, the base station 14-i can expect to receive signal S2 not before the frame boundary and not after the 2dow-radius time after the frame boundary, where dow_radius is the One-way propagation delay (or 2dow-radius is the round trip propagation delay) for a signal traveling a distance equal to the radius R ±. In this way, the search windows Wn must extend a duration of at least 2dow_radius starting at time Tn and ending not before the time Tn + 2dow-radius. In effect, the duration of the search windows Wn restricts the effective radius (or size) of the cell 18-i, which is also referred to herein as the access range of a base station. The duration of the Wn search windows depends on the implementation of the correlator. Typically, correlators are implemented in the form of an Application Specific Integrated Circuit (hereinafter referred to as an "ASIC correlator") (ASIC = Application Specific Integrated Circuit) having a predetermined number of bits (also referred to herein as "bit limitation"). ") to represent a round trip delay (of a signal traveling from the mobile telephone base station and back to the base station). This bit limitation limits the duration of the search windows, which, as discussed above, limits the effective size of the 18-i cell or access range of the base station 14-i. Provided that the bit limitation does not limit the search windows Wn to a duration less than 2dow_radius, the base station 14-i should be able to detect the S2 signal transmitted by any mobile telephone located anywhere within its cell 18-i (considering that R is the same for all points on the circumference). Implementations: typical of base stations in a CDMA wireless communication system based on IS-95, include an ASIC correlator that has a limitation of 12 bits to represent the round trip delay. In order to have fine resolution of the delay, a typical value of 1/8 PN chip is used as the minimum resolution unit. The 12-bit limitation (or round trip delay representation) in units of 1/8 PN chip produces a range of 512 PN chips (ie 212bit x 1/8 PN chip / bits). For a transmission bandwidth of 1.2288 MHz (which is typical for a CDMA wireless communication system based on IS-95), the 12-bit limitation may represent a round trip delay of 416 μs (ie, 512 chips) PN - = - 1.2288 PN chips / μs). With a propagation speed of 5.33 μs / 1,609 km (mile), the round trip delay of 416 μs (or 208 μs of one-way delay) represents the limitation that if a mobile phone is located at approximately 62.75 km (39 miles) (ie 208 μs 5.33 μs / 1,609 km (mile)) from the base station, the mobile phone is able to communicate with the base station if the radio path loss is acceptable and the search window is configured correctly - that is, the 12-bit limitation (or 512 time chip delay index representation) allows a cell with a maximum radius R ± (or a maximum round trip delay) of -about 62.75 km (39 miles). A signal transmitted by a mobile phone beyond 62.75 km (39 miles) of BS 14-i, in accordance with the prior art synchronization protocol) will not be able to reach BS 14-i within the confines of any windows of Wn search, in this way will not be reliably detectable with the 12-bit ASIC correlator. Currently, if the access range or cell size is to be extended beyond the 12-bit limitation of the ASIC correlator (ie, beyond 62.75 km (39 miles)), the ASIC correlator will have to be redesigned. Specifically, the ASIC correlator must be redesigned to increase its bit limitation in such a way that signals transmitted by mobile phones placed beyond the range of the 12-bit limitation of the ASIC correlator access range can also be detected. The redesign of the ASIC correlator however is undesirable and may not be economical for small scale applications. Therefore, there is a need to extend the cell size or access range of the base station, without having to incur the costs associated with the redesign of the ASIC correlator. COMPENDIUM OF THE INVENTION The present invention is an extended range concentric base station and a method for extending an access range or cell size without incurring ASIC correlator redesign. This is achieved with a concentric cell base station design that incorporates multiple synchronization protocols and search windows. The concentric base station has associated a micro cell and a macro cell, where the microcells and macrocells use the same frequency band but different synchronization protocols and search windows that will cause signals transmitted by mobile phones within their respective cells to be received inside the cushions of at least one search window. In one embodiment, the microcell uses the synchronization protocol of the prior art with a first search window that starts at the frame boundary and ends at some time pj. after the frame boundary, where p_x represents a time interval corresponding to a bit limitation of an ASIC mapper that is used to represent the first search window. By contrast, the macrocell uses a modified synchronization protocol and a second search window that starts after the frame boundary but not after time j. after the box border (that is, not later than the end of the first search window) and ends at some time. p2 after the second search window began, wherein the modified synchronization protocol will cause the signals transmitted by the mobile telephones in the macrocell to be received within the confines of the second search window and p_2 represents a corresponding time interval to a bit limitation of an ASIC-mapper that is used to represent the second search window. BRIEF DESCRIPTION OF THE DRAWINGS The characteristics, aspects and advantages of the present invention will be better understood with respect to the following description, appended claims and accompanying drawings wherein: Figure 1 represents a wireless communication system employing multiple code access (CDMA = Code Multiple Access) techniques based on the well-known standard IS-95; Figure 2 represents a synchronization program employed in accordance with an implementation of a synchronization protocol based on the IS-95 standard; Figure 3 represents a time diagram illustrating a sequence of transmissions and receptions by the base station and mobile telephone according to the synchronization program of Figure 2; Figure 4 represents a base station with base, in the well-known IS-95 standard for multiple access with code division employed in accordance with the present invention; Figure 5 represents a synchronization program for a synchronization protocol employed in accordance with an embodiment of the present invention; Figure 6 depicts a time diagram illustrating a sequence of transmissions and receptions by a base station and a mobile telephone located within an extension of a cell; Figure 7 represents a base station having a hierarchical cell structure employed in accordance with the present invention; Figure 8 depicts a synchronization program incorporating first and second synchronization protocols employed by the base station of Figure 7; and Figure 9 represents a base station with a micro cell and a macro cell, wherein the micro and macro cells both have an inner radius and an outer radius. DETAILED DESCRIPTION Figure 4 illustrates a base station 30 based on the well-known IS-95 standard for multiple access with code division employed in accordance with the present invention. The base station 30 includes radios and antennas for modulating and transmitting base station signals to mobile telephones and for receiving and demodulating mobile telephone signals from mobile telephones within the cell 34 and a GPS receiver to receive synchronization information using well-known global location satellites. Each radio includes a correlator implemented in the form of an ASIC (hereinafter referred to as "ASIC correlator") operable to detect mobile telephone signals, so that the mobile telephone signals can be demodulated.

For discussion purposes, the ASIC correlator has a limitation of 12 bits (or 512 PN chips) to represent a round trip delay) of a signal traveling from the base station 30 to a mobile telephone and back to the base station ( as described in the background section). This should not be considered as limiting the present invention to ASIC correlators with 12 bit limitations. It will be clear to a person of ordinary skill in the art that the present invention is equally applicable to base stations that have ASIC correlators with other bit limitations or correlators implemented in a different way than an ASIC. A 12-bit ASIC correlator (or 512 PN chips) has a search window Wn of approximately 416 μs in duration. In CDMA wireless communication systems of the prior art, which use a synchronization protocol based on the IS-95 standard, this search window W, is configured to start the Fn time (marking the beginning of frames) and end the time Fn + 416 μs, and will allow the base station 30 to detect a signal transmitted from mobile phones located within approximately 62.75 km (39 miles) of the base station 30. Thus, a mobile phone beyond 62.75 km (39 miles) of the base station 30 will be considered beyond the access range of the base station 30 equipped with a 12-bit ASIC correlator. Cell 34 has an outer radius Router (or R3) and an inner radius Rinner (° R32) where the outer radius K-ouer can be or is a distance beyond the access range of the ASIC correlator bit limitation ( for example Router >; 62.75 km (39 miles) for an ASIC correlator with a limitation of 12 bits), inner radius R? Nner is smaller than Router, and the difference? R between radios Router And Ri? Mer should not be greater than the distance (or maximum round trip delay) corresponding to the ASIC correlator bit limitation (eg,? R <62.75 km (39 miles)). In this way, part of cell 34 can go beyond the access range of the ASIC correlator bit feed. The present invention allows the base station 30 to detect signals transmitted from mobile telephones located in any part of cell 34, including beyond the access range of its ASIC correlator bit limitation (eg, beyond 62.75 km (39 miles)). )), without redesigning the ASIC correlator. The present invention is achieved by using a modified synchronization protocol which will cause the search windows to move with respect to the frame boundaries, thereby causing the signals transmitted by mobile phones located beyond the bit limitation of the ASIC correlator , are received within the search windows. This involves transmitting a base station signal at a time r relative to the frame boundaries and setting up search windows Wn to start and end at a time, and q + p, respectively, after time r, where q is a synchronization advance value greater than zero representing a propagation delay corresponding to a signal traveling no more than the round trip between the base station and the inner radius of cell 34 (i.e. - corresponds to a propagation delay for a distance greater than zero but not greater than twice the inner radius Rinner) and E represents a time interval corresponding to the ASIC correlator bit limitation or a time interval over which a Mobile phone signal can be correlated and thus detected. In one embodiment of the present invention, the base station 30 is operable to detect signals transmitted from the mobile telephone 38 using a modified synchronization protocol incorporating displaced or deflected search windows Wn. Figure 5 illustrates a synchronization program 70 for a synchronization protocol employed in accordance with this embodiment of the present invention. According to the synchronization program 70, the base station is configured to start transmitting signals at the frame boundaries and look for mobile telephone signals within displaced search windows Wn that extend from the time Fn + cj [and ending not after the time Fp + q + p. Similarly, the mobile telephone 38 is configured to start transmitting signals at some multiple x of a frame time interval (ie fx) after the mobile phones begin to receive signals from the base station. Like the synchronization program 50, the base station 30 using the synchronization program 70 will begin to receive signals transmitted from the mobile telephone 38 within the (scrolled) search window Wn. Figure 6 illustrates a time diagram 60 showing a sequence of transmissions and receptions -according to the synchronization protocol of Figure 5 by the base station 30 and the mobile telephone 38, which can be located anywhere within the cell 34. The base station 30 starts transmitting the base station signal Sx to the time Fx. The transmission of the signal Sx to the time Fn by the base station 30 will result in the reception of signals transmitted by mobile telephones 38 within the scrolled search windows Wn, so that the mobile telephone signals can be detected and demodulated by the station base 30, notwithstanding that the mobile telephone 38 is beyond the access range of the bit limitation of the ASIC correlator. The mobile phone 38 begins to receive the signal Sx_ at the time Fi + do »,, where dow is the one-way propagation delay from the base station 30 to the mobile telephone 38 (or from the mobile telephone 38 to the base station 30). Since the mobile telephone 30 is in cell 34, the propagation delay dow must correspond to a time necessary for a signal to travel at least one Rinner distance. It should be noted that for ease of discussion, the propagation delay of the station The base 38 of the mobile telephone 38 is considered identical to the propagation delay from the mobile telephone 38 to the base station 30. If the mobile telephone 38 transmits a mobile telephone signal S to the base station 30, the mobile telephone 38 expects some number of a frame time interval (ie fx) from when the mobile phone 38 begins to receive the signal Sx before it begins to transmit the signal S2. In this way, the mobile telephone 38 will begin to transmit signal S2 at some time F -? + D "," + fx (or dow time after some frame boundary). Due to the propagation delay dow from the mobile telephone 38 to the base station 30, the base station 30 will begin to receive the signal S2 at some time F1 + d ",., + Fx + d",., (Or F1 + 2dow + fx). Since 2dow corresponds to a time necessary for a signal traveling at least one round trip between the base station and a distance R? Nner the signals must be located to be received between the time Fn (ie, the frame boundary) and the time Fn + p, where p_ = 4l6 μs corresponding to the ASIC correlator bit limitation (or within the confines of the Wn search windows). The signal S2 is then detected and processed using techniques well known in the art. It should be noted that a base station incorporating only the modified synchronization protocol of the present invention may not be able to detect mobile telephone signals transmitted by mobile phones located within cell 32. To be able to detect these telephone signals mobile, the present invention uses a synchronization protocol different from the synchronization protocol used to communicate with mobile phones located within cell 34, as will be described here. Figure 7 illustrates a base station 80 having a hierarchical cell structure employed in accordance with the present invention. The base station 80 has a micro cell 82 associated with it and a macro cell 84. The micro cell 82 has a micro cell radius Rm? Cro or R82, wherein the micro cell radius RmiCro is less than or equal to a distance corresponding to the ASIC correlator bit limitation (for example Rraicro <; 62.75 km (39 miles)). The macro cell 84 has an outer cell macro R radius, macro-outer or R84 and a macro cell inner radius R •, macro-mner or RR ?, where the radius of the inner cell macro Rmacro-inner is greater than zero and less than or equal to Rmioro, and the difference? R between the macrocell radii RmaCro-outer and Rmacro-inner, nQ must _ be greater than the distance corresponding to the correlator bit limitation ASIC ( for example,? R <. 62.75 km (39 miles)) for a 12-bit ASIC correlator. Although Figure 8 shows the same cell 82 and the macrocell 84 as two separate cells, it should be understood that the microcell 82 and the macrocell 84 may also partially overlap. The base station 80 comprises a plurality of radios 90, one or more antennas 92 and a GPS receiver 94. Of the plurality of radios 90 each is operable to modulate and demodulate signals using the same frequency band freg, which includes a channel of uplink and one downlink frequency. Each radio 90 includes at least one correlator 96 implemented in the form of an ASIC. The antennas 92 are operable to transmit and receive signals using the freq frequency band. The base station 80 (or radio 90) is configured to transmit signals using the fixed frequency band such that mobile telephones located within the micro and macro cells 82, 84, receive pilot signals (transmitted by the base station 80). with an acceptable signal strength. The base station 80 provides wireless communications services to mobile telephones, such as the mobile telephone 86 in the micro cell 81 using a same frequency band freq a first synchronization protocol. The first synchronization protocol, in one modality, is the synchronization protocol currently employed in CDMA wireless communication system based on IS-95, as will be described previously in the background section. In contrast, base station 80 provides wireless communications services in mobile telephones, such as mobile telephone 88, in macro cell 84 using a second synchronization protocol, but the same frequency band. The second synchronization protocol, in one embodiment, is the aforementioned modified synchronization protocol that is illustrated in Figure 5. In this embodiment, the first synchronization protocol has a first search window associated 1-n, such that begins at the table borders and ends at some time p ^ after the table borders, where pj. represents the time interval corresponding to the bit limitation of an ASIC mapper used to represent the first search window W1-n. The second synchronization protocol has associated a second search window W2-n, which starts after the frame border but not after the time p_x after the frame borders and ends at some time p_2 after the second window started of search W2-n, where p_2 represents the time interval corresponding to the bit limitation of an ASIC correlator used to represent the second search window. A synchronization program 100 for the first and second synchronization protocols is illustrated in Figure 8, according to one embodiment. Synchronization program 100 includes a series of frames 102 -n, wherein each frame 102 -n extends a time interval f and the start of each frame 102 -n is marked by a frame boundary at time Fn aligned with GPS using the GPS receiver 94. In accordance with the first and second synchronization protocols, the base station 80 is configured to begin transmitting the base station signals using the fixed frequency band at the frame boundaries and searches for mobile telephone signals using the frequency band freq within the first search windows W1-n that extend from time Fn and do not end after the time Fp + p_? . According to the second synchronization protocol, the base station 80 is configured to begin transmitting the base station signals using the same freq frequency band at the frame boundaries, and searches for mobile telephone signals using the freq frequency band within the second search window W2- n, which start after the frame border but not after the time p_x and end at some time p_2 after the second search window started. For purposes of illustration, the second search window W2-n is illustrated as starting when the first search window W1-n ends. This should not be considered as limiting the present invention in any way. Regardless of the synchronization protocol, the mobile phones 86, 88 are configured to start transmitting signals at some x-manifold of a frame time interval (ie fx) after the mobile phones began receiving signals from the base station , where x is some integer greater than or equal to zero. When the signals arrive at the base station 80, the base station 80 will search for the input signals by the presence of mobile telephone signals using both search windows W1-n and W2-n. If the signal is transmitted by a mobile telephone in the micro cell 82, then the base station 80 will have to detect the mobile telephone signal within the first search window 1-n. If the signal is transmitted by a mobile telephone in the macro cell 84, then the base station 80 will have to detect the mobile telephone signal within the second search window W2-n. In one embodiment, the base station 80 uses different radios to search each of the search windows W1-n, W2-n. In another embodiment, the base station 80 uses a radio to search both search windows W1-n, W2_n. In yet another embodiment, the base station 80 will not search the second search window W2_n for the mobile telephone signals unless the base station 80 does not detect any mobile telephone signals in the first search window W1-n. Although the present invention has been described in considerable detail with reference to certain embodiments, other versions are possible. For example, the present invention is also applicable to base stations with a microcell and a macro cell having both indoor and outdoor radios, see Figure 9, and wireless communication systems employing other types of multiple access techniques, such as multiple access with time division. Therefore, the spirit and scope of the present invention will not be limited to the description of the modalities. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (13)

2. Having described the invention as above, the content of the following claims is claimed as property: 1. - Method for detecting a signal. mobile telephone, comprising the steps of: transmitting a base station signal at a first frame boundary; look for a mobile phone signal using a first search window starting at a second frame boundary and ending at a time px after the second frame boundary, where _x represents a time interval corresponding to a bit limitation for a first correlator; and look for the mobile phone signal using a second search window starting after the second frame boundary, but not after the time pj. after the second frame boundary and ending at time r 2 after the second search window began, where p_2 represents a time interval corresponding to a bit limitation for a second correlator. 2. - The method according to claim 1, characterized in that it further comprises the step of: detecting the mobile telephone signal using a correlator.
3. 3. - The method according to claim 2, characterized in that the mobile telephone signal is detected when a signal resulting from an input signal multiplied by known code exceeds a threshold.
4. 4. - The method according to claim 3, characterized in that the known code is a pseudo-random interference sequence.
5. 5. - The method according to claim 1, characterized in that the first frame boundary and the second frame boundary are identical.
6. 6. - The method according to claim 1, characterized in that the first frame boundary and the second frame boundary are not identical.
7. 7. - The method according to claim 1, characterized in that the step of searching for the mobile telephone signal using the second search window is performed only if the telephone signal is not detected by the stage of searching for the mobile telephone using the first search window.
8. 8. - The method according to claim 1, characterized in that the first correlator and the second correlator are the same:
9. 9. The method according to claim 1, characterized in that the first correlator and the second correlator are not
10. 10.- A base station, characterized in that it comprises: a first radio for transmitting base station signals at frame boundaries, the first radio has a first correlator configured to look for mobile telephone signals during first time intervals starting at the boundaries of frames and ending time x after the frame boundaries, where px represents a time interval corresponding to a bit limitation for the first correlator, and a second radius for transmitting base station signals at a time r relative to the frame borders, the second radio has a second correlator configured to look for mobile phone ales for seconds time intervals starting after the frame borders but not after the time px during the frame boundaries and ending at a time p_2 after it started at a time interval, where p_2 represents a time interval corresponding to a bit limitation for the second correlator.
11. 11. The base station according to claim 10, characterized in that the first correlator detects the mobile telephone signals, when a signal resulting from an input signal multiplied with a known code exceeds a threshold value.
12. 12. - The base station according to claim 11, characterized in that the second correlator detects mobile phone signals when a signal resulting from an input signal multiplied by a known code, exceeds a threshold value.
13. 13. - The base station according to claim 10, characterized in that it further comprises: a GPS receiver, to receive synchronization information to align the frame boundaries.