MXPA98008390A - Dynamic and intelligent dispersion for multiple access by division of amp band code - Google Patents

Abstract

A method is described for allocating the use of multiple carriers in a wideband CDMA (code division multiple access) transmission system, which first determines carrier usage / interference levels for each of the multiple carriers. Based on the use / interference level of the carrier, carrier assignments are determined on an unequal basis. The determination of the carrier assignment predisposes the selection of the carriers from the most highly used / interference carriers, hereinafter. An apparatus for implementing the method is also described

Description

DYNAMIC AND INTELLIGENT DISPERSION FOR MULTIPLE ACCESS BY BROADBAND CODE DIVISION Field of the Invention This invention relates to wireless communications and more particularly to code division multiple access wireless (CDMA) communications.

BACKGROUND OF THE INVENTION Wireless communication provides unimpeded access to mobile users and addresses the requirements of two specific and disjoint domains: voice telephony and internal data LAN. Cellular telephone networks have extended the domain of telephone service over a last wireless reflection path, while mobile IP LANs such as aveLA and RangeLAN do the same for internal users of TCP / IP data networks. Advances with wireless technology and wired high-speed integrated services networks promise to provide mobile users with extensive access to multimedia information in the near future. For example, Personal Communication Services (PCS) are a wide range of individualized telecommunication services that allow individuals or devices to communicate regardless of where they are at any time.

REF .: 28554 The Personal Communication Networks (PCN) are a new type of wireless telephone system that communicates via low power antennas. PCNs offer a digital wireless alternative to the traditional wired line. The following represent areas of concern in wireless technology, for example, in any wireless communication system, the power of the transmitter has a significant impact on the performance of the system. In a limited noise wireless communication system, the transmit power determines the allowable separation between the transmitter and the receiver. The available transmission power determines the signal-to-noise ratio, which must exceed some prescribed threshold at the receiver's input for a successful communication of the information to occur. When a message signal is transmitted in a communication channel, analog and digital transmission methods can be used. Digital methods are preferred because of the advantages over analogous methods, which include: increased immunity to channel noise and interference, flexible operation of the system; common format for the transmission of different kinds of message signals; improved security of communications through the use of digital encryption; and increased capacity.

Poor bandwidth utilization is another concern. A means to carry out the effective use of the available bandwidth is by means of signal multiplexing, in which signals from several message sources are transmitted simultaneously over a common spectral resource. Frequency division multiplexing, time division multiplexing and mixing have been employed to implement cellular radio systems multiplexed by signal. Another multiple access system involves the use of broadband communications, as opposed to narrowband procedures such as frequency division multiple access (FDMA) and time division multiple access (TDMA). In cellular radiotelephone systems such broadband communications have been obtained by employing code division multiple access (CDMA) scattered spectrum techniques. Such dispersed spectrum systems use a modulation technique to spread the information that is communicated over a wide frequency band. This frequency band is usually much wider than the minimum bandwidth required to transmit the information that is sent. In a direct sequence CDMA system, communication between two communication units is carried out by dispersing each transmitted signal over a wide frequency band with a single user spreading code. This results in a plurality of transmitted signals sharing the same frequency. The ability of such a system to work is based on the fact that each signal is encoded in a special way by time and / or frequency, to allow its separation and reconstruction in the receiver. The particular transmitted signals are retrieved from the communication channel by de-dispersing a signal from all signals by using a known user dispersion code related to the spread implemented in the transmitter. There is a significant investment in spectrum and equipment resources that currently support narrowband CDMA. When a broadband CDMA (W-CDMA) system using multiple carriers is superimposed on an IS-95 carrier (s), there is loss of capacity. In general, any unbalanced interference and unbalanced load across the carriers will degrade the aggregation capacity (combination or sum).

BRIEF DESCRIPTION OF THE INVENTION The present invention consists of a method for allocating the use of multiple carriers in a broadband CDMA transmission system. The method first determines the usage / interference levels of the carrier for each of the multiple carriers. Based on the use / interference level of the carrier, the carrier assignments are determined on an unequal basis. The determination of the carrier assignment predisposes the selection of the carriers from the most highly used / interfered carriers. An apparatus for implementing the method is also described.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present invention can be obtained from the consideration of the following description, in conjunction with the drawings, in which: Figure 1A is a representative spectrum for a direct dispersion forward link; Figure IB is a three-carrier forward link method representative for the W-CDMA, Figure 2 is a typical cell physical arrangement that mixes the W-CDMA cells with IS-95 cells; Figure 3 is a block diagram of a forward link of three carriers; Figure 4 is a schematic representation of the dispersion of the demultiplexer for uniform dispersion; Figure 5 is a schematic representation of an example of the unequal dispersion of the demultiplexer; Figure 6 is a graphical representation of the load utilization across the three carrier frequencies with intelligent dispersion in the forward link; and Figure 7 is a graphic representation of the load usage across the three carrier frequencies with intelligent dispersion in the reverse link.

Detailed Description of Various Illustrative Modes Although the present invention is particularly suitable for a multi-carrier W-CDMA system, such as a three-carrier W-CDMA system and will thus be described, the present invention is equally suitable for use with other carriers. multiple band carrier systems. CDMA modulation techniques have been used in communication systems to allow a large number of users to communicate with each other. In a CDMA communication system, all communication channels are multiplexed into one or several common broadband frequencies. Each channel is differentiated by a unique dispersion code. Before transmission, each information signal is modulated with a scatter code to convert the information signal to a broadband signal. A receiver demodulates the wideband signal received by combining the broadband signal with the corresponding spread code, to recover the information signal. The scatter code is usually a binary code. Since the same wide band is available to all users, information signals on other channels may appear as co-channel interference or noise when the received signal is demodulated by the scatter code. Several alternative broadband CDMA (W-CDMA) systems, which are compatible with IS-95 are currently proposed for extensive implementation. One proposal uses, in the forward link, 3 parallel 1.25 MHz carriers and disperses the coded bits uniformly over the 3 carriers for the frequency diversity. However, uniform dispersion over 3 carriers with superimposed IS-95 carrier (s) will cause some loss of capacity. In general, any known unbalanced interference and unbalanced load across the carriers will degrade the aggregation capacity (combination). The present invention uses dynamic and intelligent (non-uniform) dispersion to obtain maximum capacity in coexistence systems or systems with unbalanced interference through the carriers. By using dynamic and intelligent dispersion, the present invention provides an improved capacity with respect to uniform dispersion, in particular for the following conditions: W-CDMA superimposed with carrier (s) of IS-95; prevention of some frequencies due to the use of microwaves or any known disturbance (s) and any deterministic or statistical difference of interference through the different carriers. With reference to Figure 1A, a representative spectrum is shown for a direct spread forward link which is contrasted with a single broadband forward link. Figure IB shows a representative multiple carrier advance link method for W-CDMA systems which is compatible with IS-95 (CDMA One), which employs 3 parallel 1.25 MHz carriers (fi, f2 and f3) and disperses the bits coded equally on the 3 carriers by the diversity of frequencies. With reference to Figure 2, a cell arrangement is shown that mixes the W-CDMA cells with IS-95 cells to provide high-speed data coverage. One advantage of the multi-carrier forward link for the W-CDMA is that the capacity is less impacted in systems overlaid with IS-95. That is, because the orthogonality in the forward link can be maintained for the superimposed systems. Otherwise, similar to direct dispersion, the W-CDMA (broad band code division multiple access) and IS-95 will interfere with each other and have a significant loss in capacity. However, although orthogonality is maintained in the forward link of multiple carriers for the superimposed carrier, the forward link capability is not used efficiently. For example, suppose that the W-CDMA (broadband code division multiple access) is displayed in f? + F2 + Í3 and overlaps with IS-95 in fi. For the uniform dispersion method, the bits are uniformly dispersed to the carriers and therefore the power of use in each carrier for a specific user must be the same, due to the fact that the power control is based on the frame errors and each frame bits are uniformly dispersed to the carriers. The net effect is that the uniform dispersion method will have a greater use of aggregation power or combination in fi than in f2 and f3 due to the use of narrow band (IS-95) in fi. The associated interference in fi will then be larger and effectively costs more power per user to maintain the signal to interference ratio required. On the other hand, the intelligent dispersion method allocates more bits per user to the carriers with less interference and less load, in such a way that the associated interference in each carrier is equaled or compensated approximately in order to save energy per user and maximize the potential capacity. In IS-95, a forward link does not have a fast power control, whereas the W-CDMA (broad band code division multiple access) system described above has fast, forward power control. This means that the forward power consumption in IS-95 is much less efficient than in the W-CDMA (broadband code division multiple access). Only a few users in IS-95 can easily use up to a large portion of the forward load capacity due to power control deficiency, as well as other deployment issues (such as multiple pilot areas). As a result, the blockage in the superimposed system can occur prematurely if the W-CDMA does not use the remaining power efficiently. While it can be argued that if all three carriers are equipped with IS-95, then the load balancing can be solved, by the time the W-CDMA is introduced, it would not be practical for operators to install IS-95 systems additional for this purpose. In addition, if there are known forward link disturbances in some cell area, such as microwave users, that the system operator can not achieve mitigate or more in general, if there is a deterministic or statistical interference difference across the frequencies of W-CDMA, due to the difficulty in spectrum separation, a similar inefficient use of load / capacity will be presented. The blockage will be presented in the system before the design traffic load. In order to address this kind of unbalanced issue, the present invention uses dynamic and intelligent dispersion over the W-CDMA frequencies. Intelligent dispersion means that unequal dispersion must be based on the knowledge that wireless channels obtain the objective of maximizing the utilization of potential capacity by equalizing or compensating the load and interference through the carriers. The fundamental idea is to disperse a different amount of coded bits (ie, not uniformly) to different carriers, such that the use of power on different carriers may be different for the same user. The energy per bit is still regulated by the power control within each carrier, in such a way that the error performance can remain approximately the same. In this way, the load can be easily used to its full capacity despite some imbalance through the carriers in operation. With reference to Figure 3, a block diagram of the forward link of multiple carriers is shown. The input data is coupled to a convolution encoder and drilling system 102. The output of the convolution encoder and drilling system 102 is coupled to a symbol repetition system 104. The output or result of the symbol repetition system 104 is coupled to a block interleaver 106 (20 ms). A coding mask of length n of the user is coupled to a length code generator 110. The output of the length code generator 110 is coupled to a decimator 112. The output of the block interleaver 106 and the output of the decimator 112 are coupled to a multiplier 108. The output of the multiplier 108 is coupled to a demultiplexer 114. In the In the case of a three-carrier W-CDMA system, the demultiplexer 114 has three outputs or results A, B and C, where each output or result A, B and C is coupled to a binary circuit 116 at 4 levels. The output of the binary circuit 116 at 4 levels, the Walsh code # and the Walsh length are coupled to a corresponding Walsh coding circuit 118. The output or result of the Walsh Coding circuit 118 is coupled to a circuit 120 of Walsh. corresponding QPSK dispersion. The output of the QPSK dispersion circuit 120 is coupled to a corresponding radiofrequency amplifier 122 that produces a corresponding carrier fi, f2 or f3.

Figure 4 shows a schematic representation of the dispersion of the demultiplexer 114, wherein all the encoded bits are uniformly dispersed in 3 carriers. In other words, the dispersion is also assigned through the three frequencies, such as fi, fz r fß, fl, f2 / f3 fl f2, f3 ... O f3, f2, fi, f3, f-2 r fl / ^ 3 r ^ -Z r fi ... etc. Figure 5 shows a schematic representation of an example of the uneven dispersion of the demultiplexer 114 of the present invention. This example shows an implementation of a dispersion ratio of 1: 2: 2 for f ?: f2 f3. In other words, the dispersion is assigned equally through the three frequencies, such as fi, Í2? Í3 Í2A 3, fl, f ?? 3 / F2 / F3, F3, F2, F3, F2, F3, F2, F3, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, F2, ... The change is only in the demultiplexing function. For the data structure in frames the compensation can be used, in such a way that it fits in the transmission current. The dispersion ratio depends on the load and other known imbalance through the carriers. Intelligent dispersion refers to an algorithm to assign different dispersion ratios to different users to obtain the objective of load equilibrium. With reference to figure 6, a graphic representation of the use of charge through the three carrier frequencies with intelligent dispersion in the forward link is shown. In this particular representative mode, the fi carrier is loaded by IS-95 users while f2 and £ 3 do not have IF-95 users. Two W-CDMA users are shown in the upload. A dispersion ratio of 1: 2: 2 is assigned to user 1 for f?: F2: f3. In other words, the dispersion for user 1 is unequally assigned across the three frequencies, such as fi, f2, f3, f2, f3, fi, f2, f3, f2, f3. When an additional user, user 2, enters, the carrier fi still has a higher usage and interference than carrier f2 or carrier f3. Accordingly, the assignment is continued, to be predisposed to the carrier f2 and the carrier f3 with respect to the carrier fi. The user 2 is assigned a dispersion ratio of 1: 2: 2 for f?: F2: f3. In other words, the dispersion for user 2 is unequally assigned through the three frequencies, such as fi, f2, f3, f2, f3, fi, f ?, £ 3, f2, t3. An unequal allocation continues for additional users, the selection is predisposed from the carrier frequency that has a higher usage and interference onwards. The assignment can also be shifted to an equal allocation, as usage is balanced between the carrier frequencies. In addition, the assignment is predisposed to compensate the load caused by the known disturbances, as well as any difference or deterministic or statistical interference through the different carriers. In practice, the air interface should provide the flexibility to change the dispersion relation by sending a message from the base stations to the mobile stations (terminals). The channel assignment message and the like are the candidates to carry out the sending of this message. The message must be able to specify in detail which Walsh channels are to be used in each carrier and the dispersion relationships through the carriers. Dynamic dispersion refers to the change of dispersion relationships of a particular user with the passage of time, due to environmental variations, such as entering or leaving the disturber zone, etc. The proposed method will require that the terminal (mobile unit) for the W-CDMA perform more temporary memory storage due to the unequal dispersion between the carriers. The method described above works for the forward link. However, there are significant reasons to improve the advance link first. In the transmission of high-speed data for which the W-CDMA is proposed, the downloading of Internet data has been recognized as the dominant traffic demand. It is expected that the use of the forward link is greater than the reverse link. In the practice of 13K IS-95, it is well known that the forward link is the bottleneck in terms of capacity.

Again, slow power control and lower coding gain are the main factors. Even if the EVRC (8K) is deployed later, it is still possible (depending on the locations) that the forward link is the limiting link for capacity, due to deployment constraints, where multiple dominant pilots are prevailing. However, after improving the forward link capacity, the capacity bottleneck in the reverse link will be put into effect. For similar reasons previously described, the terminal (mobile unit) can also adopt the intelligent dispersion method, in such a way that an efficient load usage can be obtained in the reverse link. A simple way for the different dispersion in the reverse link is that the terminal (mobile unit) has the ability to transmit a signal in one of two ways, be it a 3 * 1.25 MHz (3.75 MHz) carrier or in any one of a single 1.25 MHz carrier. In other words, a terminal must be capable of dispersing a higher chip rate (3.75 MHz) and also with the lower speed option (1.25 MHz).

With reference to figure 7, a graphic representation of the use of charge through the three carrier frequencies with intelligent dispersion in the reverse link is shown. In this particular representative mode, the fi carrier is loaded by IS-95 users, while f2 and f3 have no IS-95 users. Four W-CDMA users are shown in the load. User 1 is assigned to transmit on a single 3 * f (3 * 1.25 MHz) signal, which results in an equal load of the carriers fi, f2 and f3. User 2 is assigned to transmit on a single signal 3 * f (3 * 1.25 MHz) which results in an equal load of the carriers fi, f2 and f3. User 3 is assigned to transmit to the lowest speed option on only carrier f3. User 4 is assigned to transmit in the lowest speed option in only carrier f4. An unequal assignment can be continued for additional users, with the selection predisposed from the carrier frequency that has higher utilization and interference, going forward. The assignment can also be shifted to an equal allocation as the utilization is balanced between the carrier frequencies. In addition, the assignment is predisposed to compensate for the load caused by the known disturbances, as well as any difference or deterministic or statistical interference through the different carriers.

Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art, in view of the foregoing description. Thus, this description is provided to be interpreted as illustrative only and for the purpose of teaching those in the art, the best mode for carrying out the invention. Details of the structure can be varied, substantially without deviating from the spirit of the invention, and exclusive use is reserved for all modifications, which fall within the scope of the appended claims. 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. Having described the invention as above, property is claimed as contained in the following

Claims (16)

1. Claims 1. A method for allocating the use of multiple carriers in a CDMA transmission system (broad division access code), characterized in that it comprises the steps of: determining the use / interference of the carrier wave for each of the multiple carrier waves, and determining an assignment of the carrier wave on an unequal basis; where the determination of the assignment of the carrier wave predisposes the selection of carrier waves, from the most highly used carriers / with interference, onwards.
2. 2. The method according to claim 1, characterized in that the step of determining carrier usage / interference further comprises determining the use of non-broadband CDMA carrier (multiple code division multiple access) of the multiple carriers.
3. 3. The method of compliance with the claim 1, characterized in that the step of determining the use / carrier interference further comprises determining the load caused by the known disturbances.
4. 4. The method according to claim 1, characterized in that the step of determining the use / carrier interference further comprises determining any difference or deterministic or statistical interference across the multiple carriers.
5. 5. The method according to claim 1, characterized in that the step of determining carrier use / interference further comprises determining the use of broadband CDMA (multiple division code access) carrier of the multiple carriers.
6. 6. The method according to claim 1, characterized in that the step of determining the use / carrier interference is dynamic.
7. 7. The method of compliance with the claim 1, characterized in that the step of determining the carrier assignment comprises selecting a particular carrier from the multiple less frequent carriers for a user.
8. 8. The method of compliance with the claim 1, characterized in that the step of determining the carrier assignment comprises selecting the most highly used / interfered carrier less frequent.
9. 9. An apparatus for allocating the use of multiple carriers in a broadband CDMA (code division multiple access) transmission system, characterized in that it comprises: means for determining carrier utilization / interference for each of the multiple carriers; and a demultiplexer for determining the carrier assignment on an unequal basis; wherein the demultiplexer predisposes the selection of the carriers from the carriers most highly used / with interference, thereafter. The apparatus according to claim 9, characterized in that the means for determining carrier use / interference further comprises means for determining the use of CDMA carrier (code division multiple access) without broadband, of the multiple carriers . The apparatus according to claim 9, characterized in that the means for determining carrier utilization / interference further comprises means for determining the load caused by the known disturbances. The apparatus according to claim 9, characterized in that the means for determining carrier usage / interference further comprises means for determining any difference or deterministic or statistical interference across the multiple carriers. The apparatus according to claim 9, characterized in that the means for determining carrier usage / interference further comprise determining the use of the broadband CDMA carrier (multiple division code access) carrier wave of the multiple carriers. 14. The apparatus according to claim 9, characterized in that the means for determining the use / interference of the carrier wave work dynamically. 15. The apparatus according to claim 9, characterized in that the demultiplexer selects a particular carrier from the many less frequent carriers for a user. 16. The apparatus according to claim 9, characterized in that the demultiplexer selects the most highly used / interference carrier, less frequent.