MXPA98007795A - Systems and methods of cellular communication with ba conversion - Google Patents

Abstract

The present invention offers techniques for adapting the frequency spectrum portion assigned to a Land Mobile Radio (LMR) for use as downlink cellular channels. These down-band cellular channels can be used, for example, either to complement a cellular operator system capability or as an independent cell-style system that can provide complementary geographic coverage that can, for example, form a bridge between cellular systems existing According to a first aspect of the invention, the conventional channeling of the LMR spectrum is redefined in such a way that significant advantages are obtained. More specifically, for each six originally specified 25 KHz LMR channels, five new 30KHz DBC channels are specified. In this way, in accordance with the present invention, a complete compatibility with cellular systems is achieved which allows, for example, a shift between cellular systems and D

Description

SYSTEMS AND METHODS OF CELLULAR COMMUNICATION WITH BAND CONVERSION AUTHOR DENTÉIS OF THE INVENTION The presan b > - invention refers, in general terms, to radiocommunication systems and, more specifically, to systems and methods for increasing the capacity and / or coverage areas of cellular type communication systems. The rapid growth of cellular communication systems has forced designers to look for ways in which the capacity of the system can be increased without reducing the quality of communication beyond the limits of consumer tolerance. One way through which an increased capacity can be provided is through the increase in efficiency with which the available cellular spectrum is employed, for example, by switching from analog to digital communication techniques. In North America, this change was implemented through the transition of the analog AMPS system to a digital system (D-AMPS) that was standardized as IS-54B and later as IS-136. Other technological improvements such as, for example, the implementation of Multiple Access by Time Division instead of Multiple Access by Division of Frequency, also increased the capacity of the cellular systems. Even with the implementation of more efficient technologies in terms of spectrum use, the capacity of cellular communication systems remains a concern. Another foriii? to increase the capacity of a common Bistipu i a Cellular ion = > For example, the FCC originally assigned two blocks of frequencies (ie, 825-845 MHz (uplink) and 870-B90 MHz (downlink)) for an emergency service. Cellular band in the United States of America. In 1987, the FCC allocated an additional 5 MHz to each block in order to increase the capacity of the cellular systems. The current bandwidth allocation for cellular systems in the United States, complete with channel numbering, is illustrated in the tables of Figures IA and IB. There, Figure IB shows how the central transmission frequencies can be determined for each channel described in Figure IA. And obviously, this solution has natural limits since the frequency spectrum that can be used is limited and also because other types of existing systems already have parts of the spectrum that can be used. For example, Land Mobile Radio (LMR) systems receive blocks of frequencies that are continuous to the blocks of cell-band frequencies, ie, 806-824 MHz (uplink) and 851-869 (downlink)). The conventional channel assignments for the LMR spectrum that are illustrated in the tables of Figures 2A and 2B. The sjste ss LMR are truncated transmission systems of r.id IQC uniun? > "= n: J Ó II entr *" unid -ICÍ-ÍS i diuales nnn particular organization For example, the police departments use a version of MRL (commonly known as truncated systems of public services (PST) ) For communication between patrols and exchanges, unlike Cellular systems, however, MRL systems have been historically implemented as large independent sites that receive services from one (or some) of this transmission base (s), instead of being implemented in a large geographical area that receives service from many base stations of transmission as in cellular systems, in each MRL site, an operator can receive a part of the LMR spectrum within which a fixed pair of frequencies is selected. for use as a control channel while all other frequencies can be used for traffic In 1994, the FCC announced that the frequency spectra that had been assigned for MRLs, Systems of Cellular and Personal Communications (PCS) would be regulated uniformly, in such a way that an operator can use frequencies within the joint bandwidth in any desired way. Along with other regulatory changesFor example, those that allow the leasing of LMR spectrum on a wide area basis instead of a site-by-site basis, it is now more realistic to consider the use of LMR frequencies in unconventional ways, for example, using cellular communication techniques. This use of the LMR spectrum is called here "downstream cellular use" (DBO.) To implement DBC systems that are highly compatible with cellular systems, one faces a number of challenges, for example, conventional MRL systems that operate in the The United States of America has a channel width of 25 KHz, while cellular systems operating in accordance with IS-54B have channel widths of 30 KHz. Other issues, such as interference with adjacent channels, also represent a concern COMPENDIUM OF THE INVENTION Accordingly, the present invention offers techniques for adapting the portion of the spectrum of frequencies assigned to a Land Mobile Radio (MRL) for use as down-band cellular channels.These cellular channels of l-ii rinßieii m 1 e - ± tze, par e emplo, either.; GÍ c > j? a r i a capacity of i ñteiíis e a ora ei-jiar or as a system of independent cell type that can offer a geographic coverage commentaria that can, for example, establish bridges between existing cellular systems. In accordance with a fiaspect of the present invention, the conventional division into channels of the MRL spectrum is redefined in such a way as to obtain significant advantages. More specifically, for each six originally specified 25 KHz LMR channels, five new DBC channels of 30 KHz are specified. In this way, complete compatibility with cellular systems is achieved, for example, allowing a shift between cellular systems and DBC, in accordance with the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing, and other objects, features and advantages of the present invention will be more readily undeod upon reading the following detailed description in combination with the drawings and, where; Figures IA and IB are tables showing conventional assignments of cellular band channels; Figures 2A and 2B are tables that divide the 18 MHz MRL spectrum into 25 KHz channel assignments; Figure 3A illustrates a DBC system in accordance with the pre-invention co-invention of a cellular system Figure 3B illustrates a DBC system according to the present invention which matches a conventional cellular system; Figure 4 is a block diagram of a part of an exemplary radio communication system in accordance with the present invention; Figure 5 illustrates a hypothetical mapping of conventional 25 KHz MRL channels in 30 KHz channels; Figures 6A and 6B are tables illustrating channel assignments of the LMR spectrum for DBC channels according to the present invention; Figure 7 illustrates the mapping of LMR channels in DBC channels according to the present invention at conceptual level; Figures 8-10 each illustrate a detailed example of how groups of particular MRL channels can be recanalized to provide DBC channels in accordance with the present invention; Figure 11 illustrates an uplink spectral power mask defined by the FCC to limit interference with adjacent channels and an output DBC transmission waveform generated from a remote station employing conformance transmission pulse formation t. on the invention; and The fi ura 1? a downstream power downlink defined by the FCC to limit interference with adjacent channels and an output DBC transmission waveform generated by a base station using transmission pulse training in accordance with the present invention. DETAILED DESCRIPTION The vision for downlink cellular systems includes both the supply of independent DBC systems that use the LMR spectrum and offer enhanced communication services, as well as cooperative applications of DBC systems and cellular systems. For example, Figure 3A illustrates a cooperative application of this type of DBC systems. In the figure, a DBC ß system is positioned adjacent to a cellular system. The DBC system is illustrated having a plurality of cells each of which is supported by a mobile switching center < MSC) 10. Similarly, the Cell System has a plurality of cells supported by three MSCs 12, 14 and 16. Each cell includes one or more base stations (not shown) connected to its respective MSC to transmit signals to mobile stations within the cell or to receive signals from mobile stations within the cell. In this exemplary configuration, the DBC system offers Q'Uyr Sf IC coverage? additional that allows, for example, the ope ^ acor of the? -5fce.? 4 C i > fJ3 > - offer greater geological service to your 1 lenses. Another cooperative example is illustrated in Figure 3 (b). There, each of the large circles and ellipse represents a Cellular system and each of the smaller circles within the Cellular system 20 represents a DBC system. Thus, this example illustrates a case in which DBC syεtems coincide with a Cellular System and can be used to complement the capacity of the Cellular system. Having described exemplary applications of DBC systems at the cell level, some general details of base stations and mobile stations are provided to close the comment, but without offering an unnecessary amount of detail that may obscure the present invention. Those skilled in the art will note that base stations and DBC mobile stations can be manufactured by using substantially the same components as base stations and conventional cellular mobile stations, with some exceptions, for example, the DBC equipment will have the capacity rf of operate in the LMR frequency band. Vectors interested in obtaining additional information regarding more specific details of im- munications from mobile stations and exemplary base stations are referred to the United States Patent Application opendier-d e Ha. de ne 07 / 967,07-7 titled "Mu 1 i-r'ocie Gigna i Proc s > go" j "(Procesami nto Mu 11 ¡Moc¡a] de Señales, presented on October 27, 1992 by P. Dent and B. Efcelund, which is incorporated herein by reference. DBC systems can also be implemented in accordance with D-AMPS, as is generally the case in ElA / TIA IS-54B and IS-136, which are also incorporated here by reference. Figure 4 depicts a block diagram of a part of an exemplary downlink cellular radio system in accordance with an embodiment of the present invention that can be employed to implement the foregoing. The system has an exemplary base signal 110 and a mobile station 120. The base station includes a control and processing unit 130 connected to the MSC 140 which in turn is connected to the public switched telephone network (not filtered). ). Since the DBC systems are fully compatible with cellular systems, MSC 140 can be identical to the switching equipment used in cellular systems. The base station HO for a cell includes a plurality of voice channels handled by a transceiver of voice channels 150 controlled by the control and processing unit 130. Thus, each base station includes a control channel transceiver 160 which It can handle more than one control channel. E3 control channel transceiver 160: - e control the control by 3 to a control. pro. to 130. The control transceiver 160 sends control information in the control channel of the battery station or cell to mobile stations blocked in this control channel. The voice channel transceiver manages the traffic or voice channels. When the mobile 120 enters for the first time in inactive mode, it locates a DBC control channel from which it can acquire general information and listen to hear voices. In conventional LMR systems, a control channel was identified by the processing unit 180 by tuning the voice station / control channel transceiver 170 with a control channel, said control channel being preprogrammed in the mobile station by the network operator. However, this technique is not appropriate for DBC systems where the control channels can be placed on any DBC channel frequency. Exemplary techniques for locating a DBC control channel are described in the above-incorporated US Patent Application entitled "A Method and Apparatus for Locating a Digital Control Channel in a Do? Nbanded Cellular Sysste" (Method and Apparatus for Locating a Digital Control Channel in a Descending Cell Phone System). A fechsi, the description of DBC systems is very parallel to the description of traditional cellular systems. However, the Sol i c i m te jf anf tempted numerous <; I: Bl ^ -, to adapt the portion of the spectrum MRL to that c > _. > "" > _ < n for DBC systems. The first of these difficulties refers to the historical use of channel width of 25 KHz in the LMR spectrum compared to 30 KHz channel widths that are used in many ular systems. To offer maximum equipment compatibility between DBC systems and ular systems, it is desirable to offer DBC channels that also have 30 KHz channel widths. There are many ways by which 30 KHz channels could be specified for LMR spectra. For example, each network operator could independently decide where to place 30 KHz channels based on the part or the parts of the LMR spectrum owned by that network operator. Obviously, a network operator must own at least two contiguous 25 KHz channels to provide sufficient bandwidth for a single 30 KHz channel. Since network operators in different geographical areas will often be owners of different patterns of the LMR spectrum, allowing network operators to select where the 30 KHz channels will be placed (for example, by allowing them to determine the center frequencies of each new 30 KHz channel) provide it with possibly different results since each network operator will try »op nu: H 3.I -i. -c d of your% i. For axis ~ lo. we will consider the representation of the IR spectrum illustrated in Figure 5. There, the shaded parabolas indicate channels owned by a network operator while the non-shaded parabolas represent channels owned by other operators. As you can see from the figures, this particular operator has two sets of three LMR channels of 25 KHz continuous. To optimize the capacity of the 30 KHz channels, this operator could, if allowed, locate a 30 KHz channel at any given center frequency, convert those two sets of three LMR channels into two sets of two 30 KHz channels . However, the Applicant has recognized that, even if specifically efficient, allowing network operators to select the frequencies on which the 30 KHz channels will be centered could seriously affect the compatibility between different DBC systems and between systems. DBC and yes aß ular. Without knowledge of the location of the channels of each of the systems, the displacement between them would be much more complicated. For example, it would be necessary to store a set of frequency centers for each ved operator in an EEPROM (not illustrated) in the mobile station such that the mobile station suggests what frequencies are associated with each channel number for a given network. Since the meiTt r i? EFFR0M is expensive, the solution is not efficient. By means of a lens, in accordance with one aspect of the present invention, the Applicants have specified the channel centers for DBC channels in such a way that it optimizes compatibility with existing Phones. An exemplary specification is illustrated in FIGS. 6A and 6B where the central transmitter frequencies referred to in the last two columns of FIG. 6A are illustrated by the equation in FIG. 6B. In addition to being fixed through DBC systems for compatibility purposes, the central frequencies indicated in Figures 6A and 6B have been selected for additional compliability reasons. For example, the central frequencies represented in FIGS. 6A and 6B were selected based on the known harmonics of frequency synthesis oscillators typically employed in the type in such a way that the same oscillators can be used in the DBC type to minimize the equipment costs. This is particularly valuable when the DBC equipment can handle multiple hyper bands, for example, it can operate in more than one of the LMR, ular and PCS frequency bands. By selecting the DBC channels in the manner described above in accordance with the present invention, it is possible to connect between the MRL channels of 25 I H; esμec i f? > _ ado? _, to DBC channels of r-H? Specify here. That is, for every six MRL channels of 25 kH; there are five DBC channels of 30 KHz. This concept is illustrated in Figure 7.

And indeed, in any geographical area, not all LMR frequencies can be converted into DBC channels. As mentioned above, in relation to the example of figure 5, some network operators have groups of channels and non-contiguous channels. It is interesting to note, as illustrated in Figure 8, that given the same LMR channel network owner illustrated in the upper spectrum of Figure 5, only two DBC channels according to the present invention can be created when the channels are used. DBC specified in the figure 6A and 6B. Note that in Figure 4, where the network operator was able to select the center frequencies of channels of 30 KHz, twice as many new channels of 30 KHz were obtained. This illustrates one of the compensations recognized and selected by the Applicant in accordance with the present invention - a potentially lower spectrum utilization efficiency but much better compatibility due to the uniformity of channel center locations in the systems. In Figure 8, the repetitive pattern of six MRL channels and the repetitive pattern of five DBC channels is reflected by the numbers offered directly above the parabolic and channel representations. Note that the numbers are not the real numbers of the channels and therefore are quoted in quotation marks. Central frequencies are also provided in a smaller font when appropriate. Thus, in accordance with this exemplary scenario, the LMR channels "6", "1" and "2" owned by this particular operator can only be converted into a DBC channel "i" since the bandwidths of the DBC channels u5"and" 2"fall outside the spectrum owned by the operator, although this may seem a little inefficient from the perspective of spectrum use, several techniques can be used to avoid or improve this effect of division in DBC channels. Network operators can negotiate between them to obtain contiguous LMR spectra in such a way that the DBC channeling is more efficient from a spectrum use perspective.Even if this is not possible, the referring spectrum can be used for other useful purposes. , in figure 7, the distance between central frequencies for the active DBC channel "1" and the active LMR channel "5" (after this network converter has converted the DBC channels illustrated in the spectrum lower) is 52.5 KHz. This translates into an unused band of 25 KHz, which can be used as an inherent protection band and reinforcement. Printed bands are used to provide a cushioning between adjacent channels to protect against interference from adjacent channels, which is discussed in more detail below. Alternatively, this extra bandwidth can be used to transmit signals based on alternative technologies. Even if a channel division ratio between MRL and DBC of 1 to 1 is not obtained, the possibility is foreseen that the DBC channels will be assigned according to well-known frequency rejection techniques, thus offering a substantial increase in capacity compared to the conventional use of the LMR spectrum. Other exemplary transformations of a portion of the LMR spectrum owned by an MRL operator in DBC channels are illustrated in Figures 9 and 10. In Figure 9, an operator establishes a series of five contiguous MRL channels, which can be converted into four DBC channels and a pair of contiguous LMR channels that can be converted into a single DBC channel. This figure also illustrates the minimum frequency distance between an LMR channel center and a DBC channel center. Eßto occurs when an active LMR channel of type "6" operates next to an active DBC channel of type "1". Therefore, interference considerations between adjacent channels should take into account this center-to-center distance of 27.5 KHz as described below. The other ar as, -je f ve >; > > < "Ia r-entr l DF" at central frequencies LMR p JuHri ue a protection band of 5 \ L: is provided between a DBC channel of type "4" and a channel MRL of type "6" and between a channel MRL of type "1" and a DBC channel of type "2", while there is a 15 KHz protection band on the other side of the DBC channel of type "2." In figure 10, an MRL operator has two groups of three available LMR channels for channel formations in DBC Thus, the LMR channels "4", "5" and "6" are converted into DBC channels "4" and "5." Since this MRL operator does not possess the following frequency , ie the LMR channel of type "1", a DBC channel can not be used at the next specified DBC center frequency, however, an additional protection band is provided for the next DBC channel of type "2". Given the spectral proximity between DBC channels of type "1" and LMR channels of type "6", the question arises whether or not the energy transmitted in these LMR channels will affect the reception channels on these DBC channels and vice versa. Historically, this has been a particular concern in the LMR portion of the spectrum where directly adjacent channels can be used at the same geographic location. In contrast, frequency rejection patterns are typically employed in cellular systems in such a way that the channels used at a particular site are commonly spiked, ie, for example, Z10 IH, In order to ensure that the LMR networks were to cause interference between their transmissions, the FCC has established strict emission masks that dictate the spectral energy that can be sent by a transmitter for both the uplink ( in the direction of the mobile station to the base station) as descending (from the base station to the mobile station). The masks promulgated for cellular down-band use of the LMR spectrum are likely similar to the ones illustrated by functions 1100 and 1200 in Figures 11 and 12, respectively. It is believed, however, that transmissions of conventional cellular band equipment can result in spectral energy output waveforms that violate the 1100 and 1200 masks (according to the techniques used to represent the output energy spectrum). Accordingly, in accordance with another aspect of the present invention, the following provides a technique for providing a downlink cellular equipment that complies with the masks 1100 and 1200 for operation in the LMR spectrum. In order to optimize a downlink cellular system for operation in accordance with masks 1100 and 1200, both the signal circuit and the signal transmission circuit must be set to the same signal. In this case, it is a conventional equipment, however, since another object of the present invention is to minimize the changes made to the existing cellular equipment in order to reduce this the cost of production and accelerate the implementation time, eßta exemplary mode of the present invention ß adapts only to signal transmission processing to create downlink cellular transmissions whose spectral energy outputs fall within the limits established by the máßcaraß 1100 and 1200. More specifically, by means of the transmission pulse formation filter characteristics of both the mobile station and the transmitters. For example, the waveforms 1102 and 1202 are shown in FIGS. 11 and 12, respectively, and the output paths can be used within acceptable limits. An exemplary set of transmission pulse filter characteristics employed in a Cellular system and those proposed here for a downlink cellular system for adapting the masks 1100 and 1200 are illustrated in Tables A-D below, both for uplink and downlink.

Impulse parameter TX Specification Progressive staging factor faifa) 0.35 Truncation length 48 samples Sampling rate 8 samples / symbol Window selection no window A. Cell uplink TX pulse parameter Specification SRC filter Progressive attenuation factor (alpha) 0.075 Truncation length 48 samples Sampling rate 8 uéstras / sí «bolus Window selection Kaiser window B. DBC uplink TX pulse parameter Specification Fi 11ra SRC Progressive attenuation factor (alpha) 0.35 Truncation length 90 samples Sampling rate 8 samples / symbol Window selection no window C. Downlink Cell r 'a r ii et ro of i mn ^ l ao T X Esp.ec x f n.ac i ón Filter SRC Progressive attenuation factor (alpha) 0.035 Truncation length 90 show Sample rate 8 samples / symbol Window selection of ham ing D. DBC downlink For the uplink, as can be seen above, the progressive attenuation factor of the transmission pulse filter was reduced from 0.35 to 0.075 so that the main lobe of the output power function 1102 ba e below the corner 1104 of the mask 1100. In this way, however, the side lobes 1106 of the exit function 1102 were displaced upwardly enough to violate the mask 1100. Accordingly, a window selection function was selected. Kaiser or part of the filtering methodology to suppress the side lobes in such a way that they also comply with mask 1100. Similarly, a progressive attenuation factor of 0.10 and a Hamming window selection function were selected with the object of applying the limitations required by the mask 1200 for the transmission output spectrum 1202 from the downlink t. Li.-. Exemplary embodiments described above are for the purpose of illustrating the present invention but not limiting it. Although the above exemplary embodiments have been described in terms of base stations and mobile stations, the present invention can be applied to any radio communication system. For example, satellites could transmit and receive data in communication with remote DBC devices, including portable units, personal digital assistants, etc. Furthermore, even though the present invention has been described primarily in terms of communication within the LMR spectrum, the present invention is also intended to be employed in multiple hyperband, for example, in a dual mode DBC and cellular band mobile telephony. For example, the mobile station can be implemented to operate on the side-band cellular band and a part of the LMR band. This DBC mobile station has the advantage of being able to employ existing cellular networks that allow a DBC network operator to offer a nationwide travel footprint. Readers interested in aspects of systems capable of handling multiple hyperbranches are referred to in the US Patent Application Serial No. 08 / 425,051, entitled "Multiple Perbandling Mobile Base Stations" (Mobile Stations and Battery Operational Stations). Hioerb a nf s Múltiples) of i ps er Pa i th filed on April 19, 19t 5t whose disclosure is incorporated herein by reference. Thus, a person skilled in the art can derive from the present description numerous variations in terms of the detailed implementation of the present invention. All of these variations and modifications are considered within the scope and spirit of the present invention in accordance with that defined in the following claims.

Claims (10)

1. CLAIMS 1. A method for using a portion of MRLs of a frequency spectrum, said portion of MRLs is typically used to provide truncated transection communication in channels having bandwidths of 25 KHz, to provide a cellular radiocommunication service of descending band, the method comprises the steps of: redefining said portion of LMR of the frequency spectrum to provide downlink cellular channels having bandwidth of 30 KHz; assigning, to a network operator, a plurality of downlink cellular channels of this type, said downlink cellular channels are determined based on an amount of contiguous spectrum controlled by said operator; and transmitting signals between stations in an air interface employing said downlink cellular channels allocated to provide radio communication services.
2. 2. The method of claim 1, wherein said redefinition step further comprises the step of: defining frequency. i -t- ^ > • > .-. t r-1 e ~ > e > -tnal p-tri sayings > . ai = .Is cell phones of band3 desc aí e t in accordance with the following relationship: Transmitter Channel No. Center frequency MHz Mobile 1 £ N .600 0.030 (N) + 805.980 Base 1 N < 600 0.030 (N > + 850,980
3. 3. The method of claim 2, wherein said allocation step further comprises the step of: assigning the defined down-band cellular channels encompassed by said contiguous spectrum controlled by said operator.
4. The method of claim 1, wherein said signal transmission step using said assigned downlink cellular channels further comprises the step of: filtering said signals in accordance with mask limitations in order to reduce interference with adjacent channels .
5. The method of claim 3, further comprising the step of: employing any remaining part of said contiguous spectrum that lies outside said downlink band cellular channels allocated as a protection band between said downlink cellular channels and MRL channels active assets with r > Pior sides another neridor.
6. 6. A method pa < to provide downlink cellular radiocommunication (DBC) services, comprising the steps of: defining a plurality of 30 KHz DBC channels in the frequency ranges of 806-824 MHz and 851-869 MHz at predetermined center frequencies; compare contiguous 25 KHz channels of an operator with said defined 30 KHz channels; assign a defined 30 KHz DBC channel to said operator where said comparison step indicates that said defined 30 KHz DBC channel is covered by two of the 25 kHz contiguous channels of said operator; and transmitting signals between stations in an air interface to provide said DBC radio services using said assigned 30 KHz DBC channel.
7. The method of claim 6, wherein said stations include a mobile station and a base station.
8. The method of claim 6, wherein said defining step further comprises the step of: defining said predetermined central frequencies in accordance with the following relationship: Transmitter Na. of channel Central frequency MHz Mobile 1 N ¿600 0.030 IN) + 805.980 Base 1 N _ 600. 0 < N / + 850,980
9. 9. The method of claim 6, further comprising the step of: using a remaining part of said contiguous spectrum that is outside said 30 KHz DBC channel allocated as a protection band between said assigned 30 KHz DBC channel and LMR channels assets controlled by another operator. The method of claim 6, wherein said step of transmitting signals employing said DBC channel of 30 KHz further comprises the step of: filtering said compliance signals with mask limitations in order to reduce interference with adjacent channels.