Method for allocating data elements in multicarrier applications and equipment to perform this method

• US 5,812,599 A
• Filed: 07/10/1996
• Issued: 09/22/1998
• Est. Priority Date: 07/11/1995
• Status: Expired due to Term

• Current Assignee: Alcatel NV (Nokia Corporation)
• Original Assignee: Alcatel NV (Nokia Corporation)
• Inventors: Van Kerckhove, Jean Francois
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHAYOUR, MOHAMMAD H
• Application Number:
  US08/677,468
• Time in Patent Office: 804 Days
• Field of Search: 375/260, 375/240, 375/222, 370/468
• US Class Current: 375/260
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling

Abstract

To allocate a number of data elements which constitute a data symbol to a set of carriers used for transmission in multicarrier applications, a full capacity step and capacity fine tuning step are executed successively. In the full capacity step, the individual capacity or maximum amount of data elements that may be allocated to a carrier is determined for each carrier which forms part of the set of carriers. This maximum amount of data elements is then allocated to each carrier in such a way that a full capacity occupation of the carrier set is obtained. In case of undercapacity, i.e. in case more data elements have to be allocated to the set of carriers, the capacity of the carrier set is enlarged, for example by power boosting, and additional data elements are allocated to the carriers in accordance to a predetermined rule. In case of overcapacity on the other hand, data bits previously allocated to the set of carriers, are removed from some carriers selected in accordance with another predetermined rule.

Claims

1. A method for allocating a number of data elements, grouped in a packet of data elements called a data symbol and each of said data elements comprising at least one data bit, to a set of carriers to be modulated thereon and to be transmitted via a telecommunication line, characterized in that said method includes a first, full capacity step, wherein for each carrier in said set of carriers an individual capacity number is determined, said individual capacity number being equal to a maximum amount of data elements that may be allocated to said carrier, and wherein to each said carrier said individual capacity number of data elements is allocated, and a second, capacity fine tuning step, wherein in case of undercapacity, that is, in case said number of data elements grouped in a said data symbol is larger than an overall capacity number, said overall capacity number being equal to a sum of individual capacity numbers of all said carriers, said overall capacity number is enlarged and additional data elements are allocated to said set of carriers in accordance with a predetermined capacity enlarging rule, and wherein in case of overcapacity, that is, in case said number of data elements grouped in a said data symbol is smaller than said overall capacity number, some of said data elements are removed from carriers in said set of carriers according to a predetermined data removing rule.

2. A method according to claim 1, characterized in that in said first, full capacity step, a said individual capacity number for a said carrier is obtained by comparing a signal noise ratio value measured on said carrier with required signal noise ratio values for allocating integer numbers of said data elements to said carrier, said required signal noise ratio values being listed in a required SNR per data element table.

3. A method according to claim 1, characterized in that said first, full capacity step comprises for each said carrier a first substep wherein a signal noise ratio value (SNRi) is measured on said carrier, a second substep wherein a measured signal noise ratio value (SNRi) is compared with required signal noise ratio values (SNRreq) for allocating integer numbers of said data elements to said carriers, a third substep wherein said individual capacity number is determined as being an integer number having an associated required signal noise ratio value (SNRreq) lower than said measured signal noise ratio value (SNRi) but larger than or equal to said required signal noise ratio values (SNRreq) which are lower than said measured signal noise ratio value (SNRi), and a fourth substep wherein said individual capacity number of said data elements is allocated to said carrier.

4. A method according to claim 1, characterized in that said second, capacity fine tuning step in case of undercapacity comprises a first substep wherein for each said carrier a required power boost (Bi) is calculated, said required power boost (Bi) being equal to SNRreq'"'"'-SNRi, wherein SNRreq'"'"' represents a required signal noise ratio value which allows an allocation of an additional data element to said carrier and wherein SNRi represents a signal noise ratio value measured on said carrier, a second substep wherein in said set of carriers, a carrier having a minimal required power boost (Bi) is determined, a third substep wherein a said additional data element is allocated to said carrier with said minimal required power boost (Bi), and a fourth substep wherein an overall power boost equal to said minimal required power boost (Bi) is applied to each said carrier which forms part of said set of carriers, said first, second, third and fourth substeps being repeated until said undercapacity is eliminated.

5. A method according to claim 1, characterized in that said second, capacity fine tuning step in case of overcapacity comprises a first substep wherein for each said carrier an additional noise margin (ANMi) is calculated, said additional noise margin (ANMi) being equal to SNRi-SNRreq, wherein SNRi represents a signal noise ratio value measured on said carrier, and wherein SNRreq represents a required signal noise ratio value to allow allocating to said carrier an individual capacity number of data elements, a second substep wherein in said set of carriers, a carrier having an additional noise margin (ANMi) that is minimal is determined, and a third substep wherein a data element allocated previously to said carrier with minimal additional noise margin (ANMi) is removed therefrom, said first, second and third substep being repeated until said overcapacity is eliminated.

6. A method according to claim 4, characterized in that said method further includes a pseudo-overcapacity fine tuning step executed in case a last said additional data element allocated to a said carrier in said second, capacity fine tuning step in case of undercapacity comprises more said data bits than necessary to eliminate said undercapacity, said pseudo-overcapacity step comprising a first substep wherein for each said carrier occupied by data elements which comprise less data bits than a last allocated data element an additional noise margin (ANMi) is calculated, said additional noise margin being equal to SNRi-SNRreq, wherein SNRi represents a signal noise ratio value measured on said carrier, and wherein SNRreq represents a required signal noise ratio value to allow allocating thereto the number of data elements previously allocated thereto in said full capacity step and said capacity fine tuning step, a second substep wherein among said carriers occupied by data elements which comprise less data bits than said last allocated data element, a carrier with an additional noise margin (ANMi) that is minimal is determined, and a third substep wherein a data element which comprises less data bits is removed from said carrier with minimal said additional noise margin (ANMi).

7. A program module embodied in a computer-readable medium for controlling a sequence of operations in an allocation processing unit (APU'"'"') for allocating a number of data elements, grouped in a packet of data elements called a data symbol and each of said data elements comprising at least one data bit, to a set of carriers to be modulated thereon and to be transmitted via a telecommunication line, said program module containing a set of control instructions, characterized in that said set of control instructions is structured to control said sequence of operations in said allocation processing unit (APU'"'"') in such a way that in a first, full capacity phase, for each carrier in said set of carriers an individual capacity number is determined, said individual capacity number being equal to a maximum amount of data elements allocable to said carrier, and to each said carrier said individual capacity number of data elements is allocated, and in a second, capacity fine tuning phase, in case of undercapacity, that is, in case said number of data elements grouped in a data symbol is larger than an overall capacity number, said overall capacity number being equal to a sum of individual capacity numbers of all said carriers, said overall capacity number is enlarged and additional data elements are allocated to said set of carriers in accordance to a predetermined capacity enlarging rule, and in case of overcapacity, that is, in case said number of data elements grouped in a said data symbol is smaller than said overall capacity number, some of said data elements are removed from carriers in said set of carriers according to a predetermined data removing rule.

8. An allocation processing unit (APU'"'"') provided to calculate a distribution of a number of data bits which constitute a data symbol over a set of carriers, said allocation processing unit (APU'"'"') being provided with a first input (NI'"'"') whereto said number is applied and a second input (MI'"'"') whereto carrier property information is applied, characterized in that said allocation processing unit (APU'"'"') includes a memory means (MEM) a first part (MM) for storing said carrier property information, a second part (MR) for storing carrier requirement information, and a third part (MD) for storing data allocation information, that is, an amount of said data bits for assignment to each said carrier in said set, a first comparator means (C1), coupled at its first input (C1I1) to an output (O1) of said first part (MM) of said memory means (MEM) and at its second input (C1I2) to an output (O2) of said second part (MR) of said memory means (MEM), said first comparator means (C1) for comparing said carrier property information with said carrier requirement information, for thereby obtaining individual carrier capacities for said carriers, and for applying said individual carrier capacities via an output (C1O) to a processing unit (PR) included in said allocation processing unit (APU'"'"') and coupled at an output (PO) to an input (I1) of said third part (MD) of said memory means (MEM), said processing unit (PR) for applying to said third part (MD) of said memory means (MEM) said data allocation information wherein for each said carrier said amount of data bits allocated thereto equals said individual carrier capacity of said carrier, and that said allocation processing unit (APU'"'"') further includes a second comparator means (C2), coupled at a first input (C2I1) to an output (O5) of said third part (MD) of said memory means (MEM) and at its second input (C2I2) to said first allocation processing unit input (NI'"'"'), said second comparator means (C2) for comparing said number of data bits which constitute a data symbol with an overall capacity number of said set of carriers, said overall capacity number being equal to a sum of said individual carrier capacities, and for thereby, in a capacity fine tuning step, activating said processing unit (PR) for assigning additional data elements to said carriers in accordance with a predetermined capacity enlarging rule in case of undercapacity and for removing data elements from said carriers in accordance with a predetermined data removing rule in case of overcapacity.

9. A multicarrier modulator (MOD) for modulation of data elements applied to an input (DI) thereof on a set of carriers for transmission thereof in a communication network coupled to an output (MO) thereof, said modulator (MOD) including between said input (DI) and said output (MO) a cascade connection of a mapping unit (MAP), an inverse fast fourier transform processing unit (IFFT), a cyclic prefix adder (CPA), a parallel to serial converter (PSC) and a digital to analog converter (DAC), said mapping unit (MAP) for allocating said data elements to said set of carriers and for thereby providing a frequency domain parallel sequence of data, said inverse fast fourier transform processing unit (IFFT) for inverse fast fourier transforming said frequency domain parallel sequence of data applied to its input and for thereby providing a time domain parallel sequence of data, said cyclic prefix adder (CPA) for adding a cyclic prefix to said time domain parallel sequence of data to compensate for intersymbol interference due to transmission over transmission lines in said communication network, said parallel to serial converter (PSC) for converting said time domain parallel sequence of data into a serial sequence of data for application to said digital to analog converter for transforming said serial sequence of data into an analog signal and for providing said analog signal to said output (MO) of said modulator (MOD), said mapping unit (MAP) including an allocation processing unit (APU) for providing a distribution of a number of data bits which constitute a data symbol over a set of carriers, said allocation processing unit (APU) having a first input (NI) whereto said number is applied and a second input (MI) whereto carrier property information is applied, and a data allocation unit (DAU), an input of which is coupled to said modulator input (DI) and another input of which is coupled to an output (O) of said allocation processing unit (APU), said data allocation unit (DAU) for allocating said data elements, based on said distribution provided by said allocation processing unit (APU), to said set of carriers, characterized in that said allocation processing unit (APU) includes a memory means having a first part for storing said carrier property information, a second part for storing carrier requirement information, and a third part for storing data allocation information, that is, an amount of said data bits for assignment to each said carrier in said set, a first comparator means, coupled at a first input to an output of said first part of said memory means and at a second input to an output of said second part of said memory means, said first comparator means for comparing said carrier property information with said carrier requirement information, for thereby obtaining individual carrier capacities for said carriers, and for providing said individual carrier capacities via an output to a processing unit included in said allocation processing unit (APU) and coupled at its output to an input of said third part of said memory means, said processing unit for providing to said third part of said memory means said data allocation information wherein for each said carrier said amount of data bits allocated thereto equals said individual carrier capacity of said carrier, and that said allocation processing unit (APU) further includes a second comparator means, coupled at a first input to an output of said third part of said memory means and at a second input to said first allocation processing unit input (NI), said second comparator means for comparing said number of data bits which constitute a data symbol with an overall capacity number of said set of carriers, said overall capacity number being equal to a sum of said individual carrier capacities, and for thereby, in a capacity fine tuning step, activating said processing unit for assigning additional data elements to said carriers in accordance with a predetermined capacity enlarging rule in case of undercapacity and for removing data elements from said carriers in accordance with a predetermined data removing rule in case of overcapacity.