MXPA98003689A - Allocation of frequency in a cellular telecommunications network - Google Patents

Abstract

The present invention relates to a 7- (pyrrolidinyl) -3-quinolonato-naphthyridonecarboxylic acid derivative of the formula in which X 1 represents halogen, X 2 represents hydrogen, amino, mono or dialkylamino hydroxyl, alkoxy, mercapto, alkylthio, thioarylohalogen, R 1 represents alkyl, cycloalkyl, 2-hydroxyethyl, 2-fluoroethyl, methoxy-amino, methylamino, ethylamino, dimethylamino-phenyl, R 2 represents hydrogen, alkyl, (5-methyl-2-oxo-1,3-dioxol-4-yl) -methyl; R3 represents a radical of the structure: R6 represents H, alkyl, Rn represents H, CH3-phenyl, R "represents H, CH3-phenyl, R" represents H6CH3, and represents O, -CH2, -CH2CH2 or -CH2-O, A represents N, halogenoC-R8 wherein R8 represents H, halogen, methyl, cyano, nitro, hydroxylo-methoxy

Description

ALLOCATION OF FREQUENCY IN A CELLULAR TELECOMMUNICATIONS NETWORK The present invention relates to a method for assigning carrier frequencies to base stations in a cellular radio telecommunications network, and to a radio telecommunications network that includes these frequency assignments. In known cellular radio systems, such as mobile phones, a network of base stations is provided, each having antennas. Mobile subscriber units have antennas that are necessarily omnidirectional, since subscribers often move around, both inside cells and from one cell to another. Accordingly, a frequency reuse pattern of 7 cells is common, as described, for example, in Cellular Radio Systems, Balston DM Macario RCV Editors, Artech House Inc., 1993, pages 9 to 13. A pattern of reuse of 9-cell frequency is also described in European Patent Number EP 0410831. Patent Publications Nos. O95 / 25406, WO91 / 13502 and EP 0037068, describe other different frequency assignment schemes for mobile communication. The present invention provides a cellular telecommunication network, which includes a plurality of cells distributed around a reference cell, at least two cells being allocated as they are available for the unbalanced frequency duplex communications, to the same group of pairs of RF carrier frequencies, whereby, to the greatest extent possible, different cells around the reference cell will have different orders previously preferentially determined to use the pairs of RF carrier frequencies, to substantially minimize the interference. Preferably, each cell has a predetermined order different from each other of these cells. Alternatively, where the number of frequency pairs is less than the total number of cells distributed in a ring-shaped distribution around the reference cell plus the reference cell, those cells having the same order previously determined preferably for the pairs of RF carrier frequencies, are distributed further apart, to substantially minimize the interference. The present invention has significant advantages, since the bandwidth is strictly limited. The minimization of the interference, in particular the co-channel interference, allows the reuse of frequencies, and therefore, a greater capacity of calls.

The present invention also relates to a method for selecting the use of carrier radio frequency pairs RF in a cellular telecommunications network that includes a plurality of cells distributed around a reference cell, and designated as they are available for unbalanced frequency duplex communications, to the same group of RF carrier frequency pairs, wherein, up to the largest possible degree, different cells around the reference cell have different orders previously determined preferably to use said pairs of RF carrier frequencies. The pairs of RF carrier frequencies are for duplex communications between the base stations and the subscriber units in the cells. Preferred subscriber units are at fixed locations. The transmissions are preferably by radio. A preferred embodiment of the invention will now be described, by way of example, with reference to the drawings, in which: Figure 1 is a schematic diagram illustrating the system including a base station (BTE - Base Terminator Equipment), and a subscriber unit (NTE - Network Terminator Team). Figure 2 is a diagram illustrating the structure of the frame and the timing for a duplex link.

Figure 3 is a schematic topology of part of the preferred network, showing four cells, each having a base station and subscriber units. Figure 4 is a schematic topology of a larger part of the preferred network.

Basic System As shown in Figure 1, the preferred system is part of a telephone system where the local wired exchange cycle for the subscriber has been replaced by a full duplex radio link between a fixed base station and a subscriber unit fixed. The preferred system includes the duplex radio link, and transmitters and receivers to implement the necessary protocol. There are similarities between the preferred system and digital cellular mobile phone systems, such as GSM, which are known in the field. This system uses a protocol based on a layered model, in particular the following layers: PHY (Physical), MAC (Medium Access Control), DLC (Data Link Control), N K (Network). A difference compared to GSM is that, in the preferred system, the subscriber units are in fixed locations, and there is no need for distribution configurations or other mobility-related features. This means, for example, in the preferred system, that directional antennas and main electricity can be used. Each base station in the preferred system provides six duplex radio links at twelve frequencies selected from the global frequency assignment, to minimize interference between nearby base stations. The frame structure and the timing for the duplex link are illustrated in Figure 2. Each duplex radio link comprises an uplink from a subscriber unit to a base station, and at a fixed frequency offset, a link down from the base station to the subscriber unit. The down links are multiplexed into time division (TDM), and the up links are time division multiple access (TDMA). The modulation for all links is tr / 4 - DQPSK, and the basic frame structure for all links is 10 slots per frame of 2,560 bits, that is, 256 bits per slot. The bit rate is 512 bps. The links down are transmitted continuously, and incorporate a transmission channel for the essential information of the system. When there is no user information to be transmitted, downlink transmissions continue to use the basic frame and slot structure, and contain an adequate fill pattern. For both uplink and downlink transmissions, there are two types of slots: the normal slots that are used after call establishment, and the pilot slots used during call establishment. Each normal downlink slot comprises 24 bits of synchronization information, followed by 24 bits designated as the S field, which includes an 8-bit header, followed by 160 bits designated as the D-field. This is followed by 24 bits of Forward Error Correction, and an 8-bit padding, followed by 12 bits of the transmission channel. The transmission channel consists of segments, in each of the slots of a frame, forming together in downlink common signaling channel, which is transmitted by the base station, and contains control messages containing the link information , such as slot lists, multi-frame and super-frame information, offline messages, and other basic information for system operation. During call establishment, each downlink pilot slot contains frequency correction data, and a training sequence for receiver initialization, with only a short S field, and no D field information. Link slots upwards basically contain two different types of data packet. The first type of packet, called a pilot packet, is used before a connection is established, for example, for an ALOHA call request, and to allow adaptive time alignment. The other type of data package, called a normal packet, is used when a call has been established, and is a larger data packet, due to the use of adaptive time alignment. Each normal uplink packet contains a 244-bit data packet, which is preceded and followed by a ramp of a duration of 4 bits. The remaining ramps and remaining bits of the 256-bit slot provide a guard hole against interference from the neighboring slots' due to timing errors. Each subscriber unit adjusts the timing of its slot transmissions to compensate for the time the signals need to reach the base station. Each normal uplink data packet comprises 24 bits of synchronization data, followed by an S field and a D field of the same number of bits as in each normal downlink slot. Each uplink pilot slot contains a pilot data packet that is 192 bits long, preceded and followed by 4-bit ramps that define a 60-bit extended guard slot. This larger guard hole is necessary, because there is no timing information available, and without it, propagation delays would cause neighboring slots to interfere. The pilot packet comprises 64 bits of synchronization, followed by 104 bits of the S field, which starts with an 8-bit header, and ends with a Cyclic Redundancy Check of 16 bits, 2 reserved bits, 14 bits of forward error correction (OEF, and 8 queue bits.) No field D. The S field in the aforementioned data packets can be used for two types of signaling: the first type is MAC medium access control (MS) signaling, and it is used to signal between the average access control layer of the base station, and the average access control layer of a subscriber unit, so that timing is important.The second type is called associated signaling, which can be slow or fast, and is used to signal between the base station and the subscriber units in the Data Link or Network Control layers. Field D is the largest data field, and in the case of normal telephony, with it has a digitized voice, but it can also contain samples of non-voice data. In the preferred system, provision is made for the authentication of the subscribing unit, using a challenge response protocol. General cryptic encoding is provided by combining the voice or data with an unpredictable sequence of encrypted bits produced by a key current generator that is synchronized with the superframe number transmitted. In addition, the transmitted signal is mixed to remove the DC components.

Interference There are two types of interference: co-channel interference, and adjacent channel interference, as described below. In Figure 3, a typical cell topography is illustrated. The reference cell is the one that contains the base station BTE 1. The available frequencies are divided into a number of subsets, denoted as fsl, fs2, fs3.

Co-Channel Interference The cells containing the base station BTE 1 and the base station BTE 4 operate with the same set of frequencies. Transmissions from the subscriber unit NTE 1 to the base station BTE 1 result in a co-channel interference with the base station BTE 4. The exact level of interference depends on the line loss between the two cells. However, the minimization of the transmission power from the subscriber unit NTE 1 minimizes the level of uplink interference present in the base station BTE 4.

Adjacent Channel Interference Cells containing base stations BTE 1, BTE 2, and BTE 3, have sets of mutually independent frequencies, denoted by fsl, fs2, and fs3, respectively. Each set of frequencies consists of a number of selected frequencies denoted fn, where n is increased when the frequency is increased. However, the optimal use of the available frequency sets will involve the base stations BTE 1, BTE 2, and BTE 3, which have adjacent frequencies present in the frequency sets (ie, if the selected RF frequency denoted is used) as n in the base station BTE 1, then the base station BTE 2 or BTE 3 would use the selected RF frequency denoted as n + 1). Interference is possible if the power transmitted by the subscriber unit NTE 1 in the adjacent channels (n + 1, using the previous annotation) is not sufficiently attenuated, and the line loss between the subscriber unit NTE l and the base station BTE 2 or Base station BTE 3 is low. Again, this effect can be mitigated by ensuring that the subscriber unit NTE 1 is transmitting at a power no greater than almost the minimum power for successful reception.

Reduction of Co-channel Interference Figure 4 shows the groups of RF carrier frequencies allocated among the cells in the preferred network. A group of frequencies is a range of frequencies or a selection of frequencies, or in other modalities, it can be a single frequency. In Figure 4, the reference cell is labeled CO, with its assigned frequency group denoted as C. The cells immediately adjacent to the CO cells have denoted frequency group assignments such as A, B, D, E, F , G, all different from the frequency group CO of the reference cell. However, Cl to C6 cells each have identical C group assignments for the CO cell, and consequently, cause interference if the signal from any of these cells reaches the CO cell. Each cell contains a base station and a number of subscriber units, transmitting the base station continuously (ie over the down link) over all assigned frequencies. Proper frequency planning reduces the level of interference, specifically over the uplink, that is, the signals received by the base station. To minimize the level of interference caused in the CO cell by using the same frequency group, radio frequency channel pairs are assigned to the calls in those cells in a predetermined order of RF frequency patterns. There are six preferred frequency patterns, as shown in the following table, in descending order of preference.

Ta a Each one has six pairs of RF carrier frequencies available for its base station, for communications with the subscribing units. The order in which the pairs are assigned is shown in the Table above, Cl to C6 having the same frequency group. For example, carrier frequency 1 is the first choice for the CO cell, but not for any other of the Cl to C6 cells, which have the same frequency group. In a similar way, each cell (Cl to C6, with the exception of C6), has a different order of priority. If the number of pairs of RF carrier frequencies is smaller than the number of cells having the same assigned frequency group, it is not possible to derive a unique order of assignment of pairs of RF carrier frequencies for each of these cells. Then it is necessary to consider the placement of the cells that share a group of RF frequencies, and to select the distribution of the pairs of RF carrier frequencies that minimize the possible interference. An example in the above table can be seen by comparing C6 and C3 cells. Both have identical orders of preference for the pairs of RF carrier frequencies. As shown in Figure 3, cells C6 and C3 are better separated by a greater distance between the group of cells CO to C6. The above example of the invention has been described with reference to cells having omnidirectional antennas. The invention can also be applied to cells having one or more directional antennas directed outward, such as cells having three antennas each, these antennas azimuthally directed at 120 ° apart.

Claims (14)

1. A cellular telecommunications network that includes a plurality of cells distributed around a reference cell, at least two cells being assigned as available for duplex frequency-shifted communications to the same group of RF carrier frequency pairs, characterized in that one of the less two cells have a different predetermined order of preference to use the pairs of RF carrier frequencies than the other or the other of these at least two cells, such as to reduce the interference.

2. A cellular telecommunications network according to claim 1, wherein the closest of the at least two cells have different orders previously determined preferably to use the pairs of RF carrier frequencies.

3. A cellular telecommunications network according to claim 1 or claim 2, wherein each of the at least two cells has a predetermined order different from the other of the at least two cells. A cellular telecommunications network according to claim 1 or claim 2, wherein, when the number of pairs of frequencies is less than the total number of cells next to the reference cell plus the reference cell , those of the at least two cells having the same order previously determined preferably for the pairs of RF carrier frequencies, are distributed further apart to reduce the interference. A cellular telecommunications network according to any of the preceding claims, wherein the neighboring cells are allocated as they are available for different frequency duplex telecommunication groups out of phase with the RF carrier frequency pairs. 6. A cellular telecommunications network according to any of the preceding claims, wherein the pairs of RF carrier frequencies are for duplex communications within the cells between the base stations and the subscriber units. 7. A cellular telecommunications network according to claim 6, wherein the subscriber units are in fixed places. 8. A cellular telecommunications network according to any of the preceding claims, wherein the communications are by radio. 9. A cellular telecommunications network according to any of the preceding claims, wherein messages are sent in predetermined time slots within fixed length time frames. 10. A selection method for using RF carrier radio frequency pairs in a cellular telecommunications network, including a plurality of cells distributed around a reference cell, and assigned as available for frequency-matched duplex communications to the same group of pairs of RF carrier frequencies, characterized in that each of the at least two cells around the reference cell have different orders previously determined preferably to use the pairs of RF carrier frequencies in the group. 11. A selection method for using RF carrier radio frequency pairs according to claim 10, wherein the closest of the at least two cells have different orders previously determined preferably to use the RF carrier frequency pairs. 12. A selection method for using RF carrier radio frequency pairs according to the claim 10 or with claim 11, wherein each of the at least two cells has a different predetermined order of each other of the at least two cells. A selection method for using RF carrier radio frequency pairs according to claim 11 or claim 12, wherein, when the number of frequency pairs is less than the total of the number of cells following the cell of reference plus the reference cell, those of the at least two cells having the same order previously determined preferably for the pairs of RF carrier frequencies, are further separated to reduce the interference. A selection method for using RF carrier radio frequency pairs according to any of claims 10 to 13, wherein the neighboring cells are allocated as they are available to the different groups of duplex frequency-offset communications of the carrier frequency pairs RF