(51) Int Cl.: H04L 12/56 ( )

Transcription

1 (19) Europäisches Patentamt European Patent Office Office européen des brevets (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (4) Date of publication and mention of the grant of the patent: Bulletin 06/44 (21) Application number: (22) Date of filing: (1) Int Cl.: H04L 12/6 (06.01) (86) International application number: PCT/IB04/0088 (87) International publication number: WO 04/ ( Gazette 04/2) (4) CONCATENATED FRAME STRUCTURE FOR DATA TRANSMISSION ZUSAMMENGESETZTE RAHMENSTRUKTUR FÜR EINE DATENÜBERTRAGUNG STRUCTURE DE TRAMES CONCATENEES POUR TRANSMISSION DE DONNEES (84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PL PT RO SE SI SK TR () Priority: US P US 2988 P (43) Date of publication of application: Bulletin 06/12 (73) Proprietor: Koninklijke Philips Electronics N.V. 621 BA Eindhoven (NL) (72) Inventors: DEL PRADO PAVON, Javier Briarcliff Manor, NY (US) NANDAGOPALAN, Sai Shankar Briarcliff Manor, NY (US) (74) Representative: Eleveld, Koop Jan Philips Intellectual Property & Standards, P.O. Box AE Eindhoven (NL) (6) References cited: US-B "IEEE Std b-1999; Supplement to IEEE Standard , 1999 Edition: Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band; PAGES 12-" January 00 (00-01-),, XP chapters and SYDOR JOHN: "A Proposal for a.2/.8 GHz License-Exempt (LE) WirelessHUMAN Network Standard Based on Modified IEEE a PHY and IEEE MAC standards" [Online] 1 January 01 ( ),, XP00207 Retrieved from the Internet: URL:http: // c- 01_1.pdf> chapter 2. YANG XIAO: "Concatenation and piggyback mechanisms for the IEEE MAC" 21 March 04 ( ),, PAGE(S) , XP07080 page 1643, right-hand column, line 1 - page 1644, left-hand column, last line EP B1 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 7001 PARIS (FR)

2 1 EP B1 2 Description [0001] The present invention relates to data transmission techniques, and more particularly, to an optimized method for efficiently transmitting data frames using MAC protocols, such as wireless IEEE protocol. The present invention also relates to a novel frame structure used in the inventive method. [0002] The IEEE wireless data network standard defines a Media Access Control (MAC) layer and a Physical (PHY) layer for a data network with wireless connectivity. The specification for the physical (PHY) layer specifies on how a MAC frame is transmitted over the air after adding the overheads. When a data frame arrives from the higher layer, the MAC adds the MAC layer header including addresses of the transmitter and the destination (receiver), as well as the MAC layer CRC (Cyclic Redundancy Check) known as Frame Control Sequence (FCS). Thereafter, the MAC determines the physical layer rate at which this frame is to be transmitted in the air and passes the frame to the physical layer. At this layer the frame is added with a physical layer control procedure (PLCP) header and a preamble before being transmitted in the air. The conventional frame structure is shown in Figures 1 and 2. [0003] Figure 1 illustrates a typical frame fonnat of data frames for transmission according to IEEE protocol. Each frame typically comprises two parts. One is a PLCP overhead, which includes a PLCP preamble portion 11 and a PLCP header portion 12, and the other is a MAC data frame, which includes a MAC header portion 21, a MAC frame body portion 22 and a CRC portion 23. [0004] The PLCP preamble 11 is PHY dependent, which includes information mainly used for timing and synchronization functions. The PLCP header 12 mainly includes information about the length of the frame, the transmission rate, etc. [000] The MAC data frame is illustrated in more detail in Figure 2. The MAC header Portion 21 includes addresses information 214 and other information, such as Frame Control 211, Duration/ID 212, Sequential Control 213, etc. The MAC layer CRC portion 23 is known as Frame Control Sequence (FCS). [0006] The PLCP overhead is always transmitted at the lowest transmission rates in today s IEEE systems. Specifically, the fixed transmission time is microseconds for IEEE a and g and is 192 microseconds for IEEE b. According to the current IEEE standard, the maximum size of the MAC frame is 24 bytes, and each MAC frame is added with the PLCP overhead, which substantially decreases the network throughput. Moreover, because of high error rates in wireless networks, the frames may be even fragmented into smaller fragments, and each fragment will have the above said PLCP overhead. [0007] Each MAC data frame has a MAC header 21 that includes address information 214 indicating the destination. According to the current MAC protocols such as IEEE , the address information 214 is included in the MAC header 21 in all the MAC data frames even though they are transmitted to the same destination. This does not lead to an optimized throughput efficiency. [0008] Therefore, there is a need in the art an improved method which is more efficient in transmission of MAC data frames over a data network. [0009] In one aspect, the present invention provides a new method of transmitting data frames over a data network. In particular, according to the present invention, a plural number of MAC (Media Access Control) data frames are transmitted with only a single PLCP (Physical Layer Control Procedure) overhead. Because only one PLCP overhead is transmitted with the plurality of MAC data frames, the network throughput and efficiency is considerably increased. [00] In another aspect, the present invention provides a novel frame structure of packet data to be transmitted over a data network. In particular, according to the present invention, the frame structure comprises a plural number of sequential MAC data frames and only a single PLCP overhead. [0011] Preferably, the plural MAC data frames comprise a single concatenated MAC header indicating the plural number as well as the length of MAC data frames. [0012] In a preferred embodiment, if the plural MAC data frames are transmitted to the same destination, the concatenated MAC header further indicates this common destination, and the MAC header portion in each MAC data frame is a compressed MAC header which does not include a portion indicating the destination. This further increases the network throughput and efficiency. [0013] Preferably, the frame structure does not have a limit on the size of the MAC data frames. [0014] The above and other features and advantages of the present invention will be clearer by reading the following detailed description of the preferred embodiments with reference to the accompanying drawings, in which: Figure 1 illustrates a typical frame structure of a conventional packet data for transmission over a wireless data network using IEEE protocol; Figure 2 illustrates components of the MAC data frame shown in Figure 1; Figure 3 illustrates a frame structure of an embodiment according to the present invention; and Figure 4 illustrates a frame structure of another embodiment according to the present invention. [001] According to the present invention, instead of transmitting each MAC data frame with a PLCP overhead including a PLCP preamble 11 and header 12, the MAC transmits the PLCP preamble 11 and header 12 only once before the start of the frame transmission and then transmits remaining frames without the PLCP overhead (i.e., the PLCP header 12 and pre- 2

3 3 EP B1 4 amble 11). The PLCP preamble 11 and header 12 are used by all receivers. Each receiver decodes only the MAC frames addressed to itself. This is done with the novel frame structure according to the present invention, which is a concatenated frame format (multiple frames packed into a single frame) as shown in Figure 3. [0016] As illustrated in Figure 3, a plural number of sequential MAC data frames, which are queued in the buffers, share a single PLCP overhead. This means that except for the first MAC data frame, the PLCP overhead is totally eliminated from the succeeding frames. Thus, the PLCP overhead is only transmitted once for all the plural MAC data frames. This considerably increases the efficiency and throughput of the transmission for these MAC data frames, since the PLCP overhead is always transmitted at the lowest rate. For example, if there are ten MAC data frames, the overall transmission time for these MAC data frames will be reduced by nine 9 times the single PLCP overhead transmission time. The single PLCP overhead transmission time is typical microseconds for IEEE a or g, or 192 microseconds for IEEE b. [0017] Preferably, the plurality of MAC data frames further comprises a concatenated MAC header portion 24, which provides information regarding the number of the frames following the PLCP header 12 and its length, so that the receivers will know when the MAC data frames start and end. Only one concatenated MAC header 24 is needed at the beginning of the concatenated frames. [0018] The number of the MAC data frames following the single PLCP overhead are preferably determined with consideration of the stability of the channel state. In the case where a concatenated frame is too long, it would be harmful for that frame if the channel stage changes. Based on the estimation of the future channel state during the transmission of the concatenated frame, the transmitting station may insert a PLCP preamble 11 after few frames so that the receiver using the channel state information from the preamble 11 can extract the frame if the channel were to go bad during the transmission. [0019] Figure 4 illustrates another embodiment of the present invention, in which the plural number of MAC data frames are transmitted to the same destination. In this embodiment, the concatenated MAC header 24 further indicates the common destination, while the MAC header 21 in each MAC data frame is compressed. The compressed MAC header 21 a only includes certain fields particular to each MAC frame, such as a Frame Control field 211, Sequence Control fields 213, etc, and does not include the portion indicating the common destination. Thus, the size of each MAC frame can be reduced, which further increases the network throughput and efficiency as compared to the embodiment in Figure 3. [00] Though the above has described the preferred embodiments in detail, it shall be appreciated that various changes, adaptations and amendments are possible to a skilled person in the art. For example, preferably the size of the MAC data frames is not limited to 24 bytes as required by the current IEEE standard, so the network throughput may be further improved. Moreover, the present invention is not limited to the wireless data network environment using IEEE protocol, it is also applicable to any physical media with any MAC protocol. Thus, the protection scope of the present invention is intended to be solely defined in the accompanying claims. Claims 1. A method of transmitting data frames () over a data network, comprising a step of transmitting a plural number of Media Access Control, MAC, data frames () characterized in that only a single Physical Layer Control Procedure, PLPC, overhead () is provided to all said plurality of MAC data frames (). 2. The method of claim 1, wherein said PLCP overhead () comprises a PLCP preamble (11) and a PLCP header (12). 3. The method of claim 2, wherein said MAC data frames () comprise a concatenated MAC header (24) indicating said plural number. 4. The method of claim 3, wherein said concatenated MAC header (24) further indicates a length of said plurality of MAC data frames ().. The method of claim 4, further comprising a step of inserting said PLCP preamble (11) after transmission of some of said plurality of MAC data frames (). 6. The method of claim 4, wherein said PLCP overhead () is sent with a first one of said plurality of MAC data frames (). 7. The method of claim 2, wherein each of said plurality of MAC data frames () comprises a MAC header portion (21), a MAC frame body portion (22) and a CRC (Cyclic Redundancy Check) portion (23). 8. The method of claim 7, wherein said plurality of MAC data frames () are addressed to a common destination, said concatenated MAC header (24) further indicates said destination, and said MAC header portion (21) in each data frame is a compressed MAC header (21a) that does not include a portion indicating said destination. 3

4 EP B The method of claim 1, wherein said data network is a wireless data network.. The method of claim 9, wherein said wireless data network uses IEEE protocol. 11. A frame structure of packet data for transmission over a data network, comprising: a plural number of Media Access Control, MAC, data frames (); and a Physical Layer Control Procedure, PLCP, overhead () including a PLCP preamble (11) and a PLCP header (12), characterized in that only a single one of said PLCP overhead () is provided to all said plurality of MAC data frames (). 12. The frame structure of claim 11, wherein said single PLCP overhead () is provided in front of a first one of said plurality of MAC data frames (). 1 über ein Datennetzwerk, wobei dieses Verfahren einen Verfahrensschritt umfasst zum Übertragen einer Vielzahl von "Media Access Control, MAC" Datenframes () dadurch gekennzeichnet, dass nur ein einziger "Physical Layer Control Procedure, PLCP" Overhead () allen genannten vielen MAC-Datenframes () zugeführt wird. 2. Verfahren nach Anspruch 1, wobei der genannte PLCP Overhead () eine PLCP Präambel (11) und einen PLCP Kopf (12) aufweist. 3. Verfahren nach Anspruch 2, wobei die genannten MAC Datenframes () einen verketteten MAC Kopf (24) aufweisen, der die genannte große Anzahl angibt. 4. Verfahren nach Anspruch 3, wobei der genannte verkettete MAC Kopf (24) weiterhin eine Länge der genannten Anzahl MAC Datenframes () angibt. 13. The frame structure of claim 12 wherein said MAC data frames () comprise a concatenated MAC frame header (24) indicating said plural number. 14. The frame structure of claim 13 wherein said concatenated MAC header (24) further indicates a length of said plurality of MAC data frames (). 1. The frame structure of claim 14 wherein said concatenated MAC header (24) is located between said PLCP overhead () and said first one of said plurality of MAC data frames (). 16. The frame structure of claim 12 wherein each of said plurality of MAC data frames () comprises a MAC header portion (21), a MAC frame body portion (22) and a CRC (Cyclic Redundancy Check) portion (23). 17. The frame structure of claim 16 wherein said concatenated MAC header (24) indicates a common destination of said plurality of MAC data frames (), and said MAC header portion (21) in each of said data frames is a compressed MAC header (21a) that does not include a portion indicating said common destination. 18. The frame structure of claim 17 wherein said data network is a wireless data network. 19. The frame structure of claim 18 wherein said wireless data network uses IEEE protocol Verfahren nach Anspruch 4, das weiterhin einen Schritt umfasst zum Einfügen der genannten PLCP Präambel (11) nach der Übertragung einiger Frames der genannten vielen MAC Datenframes (). 6. Verfahren nach Anspruch 4, wobei der genannte PLCP Overhead () mit einem ersten Frame der genannten vielen MAC Datenframes () gesendet wird. 7. Verfahren nach Anspruch 2, wobei jedes Frame der genannten vielen MAC Datenframes () einen Mac Kopfteil (21), einem MAC Framekörperteil (22) und einen CRC ("Cyclic Redundancy Check") Teil (23) aufweist. 8. Verfahren nach Anspruch 7, wobei die genannten vielen MAC Datenframes () zu einer gemeinsamen Bestimmung adressiert sind, wobei der verkettete MAC Kopf (24) weiterhin die genannte Bestimmung angibt, und der genannte MAC Kopfteil (21) in jedem Datenframe ein komprimierter MAC Kopf (21a) ist, der nicht einen Teil enthält, der die genannte Bestimmung angibt. 9. Verfahren nach Anspruch 1, wobei das genannte Datennetzwerk ein drahtloses Datennetzwerk ist.. Verfahren nach Anspruch 9, wobei das genannte drahtlose Netzwerk das IEEE Protokoll benutzt. Patentansprüche 11. Framestruktur von Paketdaten zur Übertragung über ein Datennetzwerk, die Folgendes umfasst: 1. Verfahren zum Übertragen von Datenframes () - eine Anzahl Media Access Control, MAC Da- 4

5 7 EP B1 8 tenframes (); und - einen Physical Layer Control Procedure, PLCP Overhead () mit einer PLCP Präambel (11) und einem PLCP Kopf (12), dadurch gekennzeichnet, dass nur ein einziger PLCP Overhead () allen Frames der genannten vielen MAC Datenframes () zugeführt wird. 12. Framestruktur nach Anspruch 11, wobei der genannte einzige PLCP Overhead () vor einem ersten Frame der genannten vielen MAC Datenframes () vorgesehen ist. 13. Framestruktur nach Anspruch 12, wobei die genannten MAC Datenframes () einen verketteten MAC Framekopf (24) aufweisen, der die genannte große Anzahl angibt. 14. Framestruktur nach Anspruch 13, wobei der genannte verkettette MAC Kopf (24) weiterhin eine Länge der genannten vielen Frames der MAC Datenframes () angibt. 1. Framestruktur nach Anspruch 14, wobei der genannte verkettete MAC Kopf (24) sich zwischen dem genannten PLCP Overhead () und dem genannten ersten Frame der genannten vielen MAC Datenframes () befindet. 16. Framestruktur nach Anspruch 12, wobei jedes Frame der genannten vielen MAC Datenframes () einen MAC Kopfteil (21), einen MAC Framekörperteil (22) und einen CRC-Teil ("Cyclic Redundancy Check") (23) aufweist. 17. Framestruktur nach Anspruch 16, wobei der genannte verkettete MAC Kopf (24) eine gemeinsame Bestimmung der genannten vielen MAC Datenframes () angibt, und wobei der genannte MAC Kopfteil (21) in jedem der genannten Datenframes ein komprimierter MAC Kopf (21a) ist, der keinen Teil aufweist, der die genannte gemeinsame Bestimmung angibt. 18. Framestruktur nach Anspruch 17, wobei das genannte Datennetzwerk ein drahtloses Datennetzwerk ist. 19. Framestruktur nach Anspruch 18, wobei das genannte drahtlose Netzwerk das IEEE Protokoll benutzt de transmission d un nombre plural de trames de données de Commande d Accès au Support, MAC, () caractérisé en ce que seulement un seul surdébit de la Procédure de Commande de la Couche Physique, PLCP, () est fourni pour toute ladite pluralité de trames de données MAC (). 2. Procédé selon la revendication 1, dans lequel ledit surdébit PLCP () comprend un préambule PLCP (11) et un entête PLCP (12). 3. Procédé selon la revendication 2, dans lequel lesdites trames de données MAC () comprennent un entête concaténé MAC (24) indiquant ledit nombre plural. 4. Procédé selon la revendication 3, dans lequel ledit entête concaténé MAC (24) indique en outre une longueur de ladite pluralité de trames de données MAC ().. Procédé selon la revendication 4, comprenant en outre une étape d insertion dudit préambule PLCP (11) après transmission de quelques trames de ladite pluralité de trames de données MAC (). 6. Procédé selon la revendication 4, dans lequel ledit surdébit PLCP () est envoyé avec une des premières trames de ladite pluralité de trames de données MAC (). 7. Procédé selon la revendication 2, dans lequel chacune de ladite pluralité de trames de données MAC () comprend une partie d entête MAC (21), une partie de corps de trame MAC (22), et une partie de CRC (Vérification de Redondance Cyclique) (23). 8. Procédé selon la revendication 7, dans lequel ladite pluralité de trame de données MAC () est adressée à un destinataire commun, dans lequel ledit entête concaténé MAC (24) indique en outre ladite destination, et dans lequel ladite partie d entête MAC (21) dans chaque trame de données est un entête MAC compressé (21a) qui n inclus pas une partie indiquant ladite destination. 9. Procédé selon la revendication 1, dans lequel ledit réseau de données est un réseau de données sans fil.. Procédé selon la revendication 9, dans lequel ledit réseau de données sans fil utilise le protocole IEEE Revendications 1. Procédé de transmission de trames de données () sur un réseau de données, comprenant une étape 11. Une structure de trames de données en paquet pour transmission sur un réseau de données comprenant :

6 9 EP B1 un nombre plural de trames de données de Commande d Accès au Support MAC () et un surdébit () de Procédure de Commande de la Couche Physique PLCP comprenant un préambule PLCP (11) et un entête PLCP (12), un seul dudit surdébit PLCP étant prévu pour toute ladite pluralité de trames de données MAC (). 12. Structure de trames selon la revendication 11, dans laquelle ledit seul surdébit PLCP ) est prévu au début de la première de ladite pluralité de trames de données MAC (). 13. Structure de trames selon la revendication 12, dans laquelle lesdites trames de données MAC () comprennent un entête (24) de trames MAC concaténées indiquant ledit nombre plural Structure de trames selon la revendication 13, dans laquelle ledit entête de MAC concaténées (24) indique en outre une longueur de ladite pluralité de trames de données MAC (). 1. Structure de trames selon la revendication 14, dans laquelle ledit entête de MAC concaténées (24) est situé entre ledit surdébit PLCP () et ledit premier de ladite pluralité de trames de données MAC () Structure de trames selon la revendication 12 dans laquelle chacune de ladite pluralité de trames de données MAC () comprend une partie d entête MAC (21), une partie de corps de trame MAC (22), et une partie de CRC (Vérification de Redondance Cyclique) (23) Structure de trames selon la revendication 16 dans laquelle ledit entête de MAC concaténées (24) indique une destination commune de ladite pluralité de trames de données MAC (), et dans lequel ladite partie d entête MAC (21) dans chacune des dites trames de données est un entête MAC compressé (21a) qui n inclus pas une partie indiquant ladite destination. 18. Structure de trames selon la revendication 17, ledit réseau de données étant un réseau de données sans fil. 19. Structure de trames selon la revendication 17, ledit réseau de données sans fil utilisant le protocole IEEE

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