WO2003081800A1

WO2003081800A1 - Combination of a frequency hopping method and ofdm

Info

Publication number: WO2003081800A1
Application number: PCT/DE2003/000832
Authority: WO
Inventors: Kai Lewandowski; Anton Kruk
Original assignee: Siemens Aktiengesellschaft
Priority date: 2002-03-27
Filing date: 2003-03-14
Publication date: 2003-10-02
Also published as: AU2003223870A1; DE10213873A1

Abstract

The aim of the invention is to increase the bandwidth during transmission using a frequency hopping method. To achieve this, several subscribers gain multiple access to a data channel and the carrier frequency is modified several times during the transmission in said data channel. The data must be at least partially transmitted using a multi-carrier system, whose carrier frequencies are modified during transmission. The advantages of frequency hopping can thus also be applied to OFDM systems.

Description

Combination of frequency hopping with OFDM

The present invention relates to an apparatus and a method for transmitting data by multiple access to a data channel by one or more participants and multiple changes of the carrier frequency during the transmission in the data channel.

The HomeRF architecture is characterized by a combination of data transport systems with asynchronous "best-effort ^Λ - from mechanisms asynchronous priority mechanisms and / or isochronous transfer mechanisms. The isochronous mechanism allows hardly any signal fluctuations and delays and is therefore particularly intended for voice transmission. The asynchronous priority mechanism is primarily used for the transmission of audio and video data. The asynchronous "best effort *" mechanism, on the other hand, is used for the less time-critical data exchange, the transmission quality compared to the other two mechanisms, especially with regard to possible delays, being low.

Such requirements are placed on data transmission systems, particularly in in-house systems. Appropriate

Specifications for this are summarized in Standard HomeRF Specification, Revision 2.0 Draft 2001 05 07 by “The HomeRF Technical Committee ^{, Λ} .

HomeRF systems are based on single carrier transmission methods. The data are transmitted at different data rates. At the low rate (LR), the symbol clock is 800 kHz, while the symbol clock at high data rate (HR) is 5 MHz.

The physical layer (phy layer) according to the HomeRF standard defines several data formats, including one Data format in which both the low transmission rate and the high transmission rate are used in a data packet. This data format is shown in Figure 1 and can be found in the HomeRF standard _, on page 63. The individual data elements of this data format are not dealt with here and reference is instead made to the corresponding figure description on page 62 of the HomeRF standard. What is important in this context is only the fact that the data packet has a low-rate portion, which is designated with "LR 2-FSK" and a higher-rate portion, which is designated with "HR 4-FSK". The shares are modulated with 2-FSK or 4-FSK (Frequency Shift Keying). The narrowband part LR 2-FSK and the broadband part HR 4-FSK are separated by a gap (GAP).

HomeRF systems usually use a frequency hopping method for transmission. The radio transmission method, also known as “Frequency Hopping Spread SpectruπT (FHSS)”, is based on more or less frequent changes in radio frequencies. Due to these frequency jumps, a larger frequency spectrum is required for radio transmission. Several participants share the total bandwidth of the system. This procedure increases security against eavesdropping and interference. In addition, a uniform energy distribution over the frequency spectrum used is guaranteed.

The so-called "HomeRF Medium Access Control Layer ' ^λ defines the procedures that determine access to the radio medium. These procedures enable TDMA (Time Division Multiple Access) priority access for isochronous data. A CSMA priority access (carrier sense multiple access) is provided for asynchronous data, so-called “streaming data”. The object of the present invention is to increase the transmission bandwidth in such multiple access systems with frequency hopping methods.

According to the invention, this object is achieved by a method for transmitting data by multiple access to a data channel by one or more subscribers and multiple changes of the carrier frequency during the transmission in the data channel, the data being transmitted at least in part with a multi-carrier system, the carrier frequencies of which during the transmission change.

In addition, the above-mentioned object is achieved by a device for transmitting data with a multiple access device, through which multiple access to a data channel can be carried out by one or more participants, and a control device for changing the carrier frequency during transmission in the data channel, and a multicarrier transmission device with which the data can be transmitted at least partially on a plurality of carriers, the respective carrier frequencies being changeable by the control device in accordance with a predetermined order.

Advantageous developments of the inventions result from the subclaims.

The invention is based on the idea that only "single carrier * methods are currently used in HomeRF systems and that, according to the invention," multi carrier * methods (multi-carrier methods) can now also be used for data transmission to increase the data throughput, with frequency hopping * being retained.

The integration of OFDM (Orthogonal Frequency Division Multiplexing) in a frequency hopping system, such as the HomeRF system, has proven to be particularly favorable while maintaining the already known “single carrier” voice service. So there is a certain backward compatibility.

The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

1 shows a data format used in HomeRF systems; and

Figure 2 is a schematic representation of a frequency hopping in an OFDM channel.

The exemplary embodiments described below represent preferred embodiments of the present invention.

FIG. 2 schematically shows a data frame consisting of a single-carrier portion 1 and a multi-carrier portion 2. Time-critical data is transmitted in the single-carrier portion 1, while data which are less time-critical, such as audio, are transmitted in the multi-carrier portion 2. and video data.

The bandwidth of the multicarrier portion 2 to which OFDM is applied is greater than that of the single carrier portion 1. This results directly from the graphic in which the frequency is plotted on the ordinate. The frequency bands of the single-carrier portion 1 and the multi-carrier portion 2 have the same center frequency f1.

After the data unit consisting of parts 1 and 2 has been transmitted, a frequency jump from frequency fl to frequency f2 takes place at time t1. The data unit subsequently transmitted usually consists, like the previous one, of a single carrier portion 11 and a multi-carrier portion 12. The center frequency of the two portions 11 and 12 corresponds to the frequency f2. This means that the multicarrier portion 2.12 to which OFDM is applied does not remain at one frequency, but also on ..Frpσiipnrv Hnn- ping * participates, whereby the single carrier portion 1.11 is arranged in the middle of the OFDM channel for the multi-carrier portion 2.12.

Because the multicarrier component 2.12 also performs the frequency jump, the synthesizer does not have to swing around when switching between single-carrier and multicarrier transmission. This results in a significant simplification in the hardware implementation.

In addition, the participation of the multicarrier or OFDM portion 2.12 in “frequency hopping” means that the advantages of “frequency hopping” also apply to the OFDM portions. In addition to the reduced susceptibility to interference, these are in particular the even distribution of the energy over the frequency band used.

The TDMA method is particularly suitable as the access method for the individual carrier portion 1, 11, while the CSMA method is primarily used for the individual carrier portion 2, 12.

In the above embodiment, in addition to the multicarrier component 2, 12, a single carrier component is used for isochronous services. According to the invention, a data unit can also consist only of a multi-carrier component to which frequency hopping is applied. Furthermore, another multi-carrier method can always be used instead of the OFDM method mentioned above.

Claims

claims

1. Procedure for transferring data through

Multiple access to a data channel by one or more participants and

multiple changes of the carrier frequency during the transmission in the data channel,

d a d u r c h g e k n n z e i c h n e t, d a s s

the data are transmitted at least partially (2.12) with a multi-carrier system, the carrier frequencies of which are changed during the transmission.

2. The method according to claim 1, wherein part of the data (1,11) is transmitted in a single carrier system.

3. The method according to claim 1 or 2, wherein a part of the data (2,12) is transmitted by the multiple access method CSMA.

4. The method according to claim 3, wherein the part of the data (2, 12) transmitted by CSMA compared to TDMA (1, 11) transmitted with lower quality with regard to the real-time requirement, in particular with the quality level "best effort * according to "HomeRF specification *, is transmitted.

5. The method according to any one of claims 1 to 4, wherein voice data are transmitted with a single carrier.

6. The method according to any one of claims 1 to 5, wherein the multi-carrier system is an OFDM system.

7. The method according to any one of claims 2 to 6, wherein the frequency band of the single carrier system is substantially in the middle (fl, f2) of the frequency band of the multi-carrier system.

8. Device for transmitting data with

Multiple access device, by which multiple access to a data channel can be carried out by one or more participants, and

a control device for changing the carrier frequency during transmission in the data channel,

marked by

a multicarrier transmission device with which the data can be at least partially (2, 12) transmitted on a plurality of carriers, the respective carrier frequencies being changeable by the control device in accordance with a predetermined order.

9. The device according to claim 8, which comprises a single-carrier transmission device with which part of the data can be transmitted in a single-carrier system.

10.The device according to claim 8 or 9, wherein the multiple access device comprises a CSMA unit with which at least some of the data (2, 12) can be transmitted.

11.Device according to claim 10, wherein the quality of the transmission with respect to the real-time requirement can be controlled by the CSMA unit.

12. Device according to one of claims 8 to 11, wherein the multicarrier transmission device is an OFDM device.

13.Device according to one of claims 9 to 12, wherein the frequency band of the single carrier system is arranged in the middle of the multi-carrier system.