CA2753721A1 - Channel estimation in an ofdm transmission system - Google Patents
Channel estimation in an ofdm transmission system Download PDFInfo
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- CA2753721A1 CA2753721A1 CA2753721A CA2753721A CA2753721A1 CA 2753721 A1 CA2753721 A1 CA 2753721A1 CA 2753721 A CA2753721 A CA 2753721A CA 2753721 A CA2753721 A CA 2753721A CA 2753721 A1 CA2753721 A1 CA 2753721A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0226—Channel estimation using sounding signals sounding signals per se
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
- H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
- H04L25/0232—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals
- H04L25/0234—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals by non-linear interpolation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
Abstract
A method of channel estimation in an OFDM transmission system having a transmitter and a receiver according to standard IEEE 802.11x, comprising, in the transmitter, setting an identifier in the reserved bits section of the header following the preamble in a physical layer frame, attaching a postamble at the end of said frame without altering the length information in the header, and transmitting said frame over the channel; and in the receiver, checking said reserved bits section in the header of a frame received over the channel for said identifier and, if said identifier is detected, using the postamble and the preamble of the frame to estimate the channel.
Description
Channel Estimation in an OFDM Transmission System The present invention relates to a method of channel esti-mation in an OFDM transmission system having a transmitter and a receiver according to standard IEEE 802.11x.
Car-to-car and car-to-infrastructure systems are currently being standardized. All standards on the dedicated 5.9 GHz band base on IEEE 802.11 and the extensions particularly devised for vehicle use, 802.11p. These extensions are limited to halving the bandwith, and by that having a longer cyclic prefix. In the present disclosure the term "IEEE 802.llx" refers to all vari-ants and extensions of the basic standard IEEE 802.11.
A significant problem in the mobile radio channel is the fast variation of the channel over time. These variations need to be tracked by the receiver to achieve a trustworthy estimate of the channel in order to coherently decode the symbols. The current channel training sequence ("pilot sequence") that is used in IEEE 802.llx is not well suited for this problem. The reason for this shortcoming in the standard was that IEEE
802.llx was initially designed for nomadic applications (WiFi on laptop computers or smart phones), where mobility is nomadic only.
Still, the IEEE 802.11x pilot pattern was chosen for the ITS standards - the reason is simply that chipsets are already available on the market. These chipsets will initially achieve only reduced performance in non-line-of-sight and highly-mobile environments. Thus, an improvement of the current standards is vital to enable robust communications for safety-related commu-nications.
The main problem of an extension of the standard is to stay compatible with older chipsets due to the long lifetime of cars. Improvements to the standard should be backwards compati-ble such that already deployed chipsets do not need to be changed.
Car-to-car and car-to-infrastructure systems are currently being standardized. All standards on the dedicated 5.9 GHz band base on IEEE 802.11 and the extensions particularly devised for vehicle use, 802.11p. These extensions are limited to halving the bandwith, and by that having a longer cyclic prefix. In the present disclosure the term "IEEE 802.llx" refers to all vari-ants and extensions of the basic standard IEEE 802.11.
A significant problem in the mobile radio channel is the fast variation of the channel over time. These variations need to be tracked by the receiver to achieve a trustworthy estimate of the channel in order to coherently decode the symbols. The current channel training sequence ("pilot sequence") that is used in IEEE 802.llx is not well suited for this problem. The reason for this shortcoming in the standard was that IEEE
802.llx was initially designed for nomadic applications (WiFi on laptop computers or smart phones), where mobility is nomadic only.
Still, the IEEE 802.11x pilot pattern was chosen for the ITS standards - the reason is simply that chipsets are already available on the market. These chipsets will initially achieve only reduced performance in non-line-of-sight and highly-mobile environments. Thus, an improvement of the current standards is vital to enable robust communications for safety-related commu-nications.
The main problem of an extension of the standard is to stay compatible with older chipsets due to the long lifetime of cars. Improvements to the standard should be backwards compati-ble such that already deployed chipsets do not need to be changed.
2 -It is an object of the present invention to devise a meth-od of channel estimation in an OFDM system according to IEEE
802.llx which is backwards compatible and has an improved esti-mation performance suited for fast varying channels in vehicu-lar environments.
This object is achieved with a method of channel estima-tion in an OFDM transmission system having a transmitter and a receiver according to standard IEEE 802.11x, comprising:
in the transmitter, setting an identifier in the reserved bits section of the header following the preamble in a physical layer frame, attaching a postamble at the end of said frame without altering the length information in the header, and transmitting said frame over the channel, in the receiver, checking said reserved bits section in the header of a frame received over the channel for said iden-tifier and, if said identifier is detected, using the postamble and the preamble of the frame to estimate the channel.
The invention enables the beneficial use of postambles within the framework of conventional IEEE 802.11x standards by extending the 802.llx pilot pattern. The postamble added to the frame is announced in a to-date unused packet header field. The extension is done in a transparent way, such that conventinal receivers (not knowing about the new pilot pattern) maintain their performance. However, receivers taking the new pattern into account have two major advantages: (i) significantly in-creased receiver performance in terms of BER (bit error rate), and (ii) significantly lower receiver complexity. The result is a tremendous reduction of implementation complexity for achiev-ing a good system performance.
The benefits of using a postamble in addition to a pream-ble for channel estimation purposes is known in the art per se, see e.g. US 2009/0209206 Al; S. Plass et al. (eds.), "Channel estimation by exploiting sublayer information in OFDM systems", Multi-Carrier Spread Spectrum 2007, pp. 387-396, 2007 Springer;
and S. Rossi and R.R. Muller, "Slepian-based two-dimensional
802.llx which is backwards compatible and has an improved esti-mation performance suited for fast varying channels in vehicu-lar environments.
This object is achieved with a method of channel estima-tion in an OFDM transmission system having a transmitter and a receiver according to standard IEEE 802.11x, comprising:
in the transmitter, setting an identifier in the reserved bits section of the header following the preamble in a physical layer frame, attaching a postamble at the end of said frame without altering the length information in the header, and transmitting said frame over the channel, in the receiver, checking said reserved bits section in the header of a frame received over the channel for said iden-tifier and, if said identifier is detected, using the postamble and the preamble of the frame to estimate the channel.
The invention enables the beneficial use of postambles within the framework of conventional IEEE 802.11x standards by extending the 802.llx pilot pattern. The postamble added to the frame is announced in a to-date unused packet header field. The extension is done in a transparent way, such that conventinal receivers (not knowing about the new pilot pattern) maintain their performance. However, receivers taking the new pattern into account have two major advantages: (i) significantly in-creased receiver performance in terms of BER (bit error rate), and (ii) significantly lower receiver complexity. The result is a tremendous reduction of implementation complexity for achiev-ing a good system performance.
The benefits of using a postamble in addition to a pream-ble for channel estimation purposes is known in the art per se, see e.g. US 2009/0209206 Al; S. Plass et al. (eds.), "Channel estimation by exploiting sublayer information in OFDM systems", Multi-Carrier Spread Spectrum 2007, pp. 387-396, 2007 Springer;
and S. Rossi and R.R. Muller, "Slepian-based two-dimensional
3 -estimation of time-frequency variant MIMO-OFDM channels", IEEE
Signal Process. Lett., vol. 15, pp. 21-24, January 2008. Pre-and postambles can e.g. be used as input to a 2-dimensional Wiener Filter estimating the channel parameters over frequency and time. Therefore, in one embodiment of the invention the channel is estimated by 2-dimensional interpolation in time and frequency between the preamble and the postamble by means of a Wiener Filter.
The identifier announcing the postamble for receivers ca-pable of handling the postamble can be set in any of the re-served bits of the IEEE 802.11x physical layer frame header. In a first embodiment, the identifier is a flag in the reserved.
bit of the signal section of the header. Alternatively, the identifier is a code which is set in one or more of the re-served bits of the service bits section of the header.
The postamble can be any given set of data suited for channel estimation purposes. Preferably, the postamble is an OFDM symbol containing a known pilot pattern, as will be rea-dily aware to the person skilled in the art.
While the method of the invention is basically suited for all variants of IEEE 802.11x, it is particularly suited for ap-plication in OFDM transmission systems according to the IEEE
802.11p standard for highly mobile environments.
The invention will now be described further by means of exemplary and preferred embodiments thereof under reference to the enclosed drawings, wherein:
Figs. 1 and 2 show pilot patterns according to the stand-ard IEEE 802.11x and according to the method of the invention, respectively;
Fig. 3 shows the incorporation of the postamble and its identifier in the physical layer frame of an OFDM transmission scheme according to the invention for use in the inventive channel estimation method; and Fig. 4 shows the performance of the inventive method in comparison to conventional channel estimation methods.
Signal Process. Lett., vol. 15, pp. 21-24, January 2008. Pre-and postambles can e.g. be used as input to a 2-dimensional Wiener Filter estimating the channel parameters over frequency and time. Therefore, in one embodiment of the invention the channel is estimated by 2-dimensional interpolation in time and frequency between the preamble and the postamble by means of a Wiener Filter.
The identifier announcing the postamble for receivers ca-pable of handling the postamble can be set in any of the re-served bits of the IEEE 802.11x physical layer frame header. In a first embodiment, the identifier is a flag in the reserved.
bit of the signal section of the header. Alternatively, the identifier is a code which is set in one or more of the re-served bits of the service bits section of the header.
The postamble can be any given set of data suited for channel estimation purposes. Preferably, the postamble is an OFDM symbol containing a known pilot pattern, as will be rea-dily aware to the person skilled in the art.
While the method of the invention is basically suited for all variants of IEEE 802.11x, it is particularly suited for ap-plication in OFDM transmission systems according to the IEEE
802.11p standard for highly mobile environments.
The invention will now be described further by means of exemplary and preferred embodiments thereof under reference to the enclosed drawings, wherein:
Figs. 1 and 2 show pilot patterns according to the stand-ard IEEE 802.11x and according to the method of the invention, respectively;
Fig. 3 shows the incorporation of the postamble and its identifier in the physical layer frame of an OFDM transmission scheme according to the invention for use in the inventive channel estimation method; and Fig. 4 shows the performance of the inventive method in comparison to conventional channel estimation methods.
- 4 -The present method is based on the IEEE 802.11 standard and all its variants, improvements and extensions, herein com-prised by the general denominator "802.11x", including stand-ards 802.11a, 802.11b, 802.11g, 802.11n, 802.11p, et cet. All IEEE documents defining those standards are herein incorporated by reference.
. The current structure of an OFDM frame (data packet) in IEEE 802.11p is shown in Fig. 1 comprising 52 subcarriers in the frequency range over symbol time. The first two (actually:
more than two) OFDM symbols are used as training symbols ("pre-amble") containing known pilots. Then, throughout the whole frame, only 4 subcarriers are used as pilots for phase and clock tracking.
Figs. 2 and 3 show an improved pilot pattern and an im-proved physical layer (PHY) frame (data packet) for an improved channel estimation method in an OFDM transmission system ex-tending the standard IEEE 802.11x, in particular 802.11p. At the end of a conventional physical layer frame 2 preceded by a preamble 1 according to IEEE 802.11x, a postamble 3 is attached which consists of one or more OFDM symbols containing a known pilot pattern. While postamble 3 does change the physical length of the frame 2, the LENGTH information in the header "PLCP" (Physical Layer Convergence Procedure-header) 5 of the frame 2 is not changed with respect to its conventional (Fig.
1) use and value. Therefore, conventional receivers will ignore postamble 3.
One or more of the reserved bits in the reserved bits sec-tion of the PLCP header 5 is/are used to set an identifier 4 therein which indicates the existence of postamble 3. The iden-tifier 4 can be a flag set in a single bit of the "Reserved SERVICE Bits" section of the PLCP header 5, as shown in Fig. 3 for bit 15, or a flag set in the single "Reserved 1 bit" fol-lowing the 4 RATE bits in the PLCP header 5. Alternatively, more than 1 bit could be used of the available (in total: 1 +
9) reserved bits of the PLOP header 5 to set a code therein
. The current structure of an OFDM frame (data packet) in IEEE 802.11p is shown in Fig. 1 comprising 52 subcarriers in the frequency range over symbol time. The first two (actually:
more than two) OFDM symbols are used as training symbols ("pre-amble") containing known pilots. Then, throughout the whole frame, only 4 subcarriers are used as pilots for phase and clock tracking.
Figs. 2 and 3 show an improved pilot pattern and an im-proved physical layer (PHY) frame (data packet) for an improved channel estimation method in an OFDM transmission system ex-tending the standard IEEE 802.11x, in particular 802.11p. At the end of a conventional physical layer frame 2 preceded by a preamble 1 according to IEEE 802.11x, a postamble 3 is attached which consists of one or more OFDM symbols containing a known pilot pattern. While postamble 3 does change the physical length of the frame 2, the LENGTH information in the header "PLCP" (Physical Layer Convergence Procedure-header) 5 of the frame 2 is not changed with respect to its conventional (Fig.
1) use and value. Therefore, conventional receivers will ignore postamble 3.
One or more of the reserved bits in the reserved bits sec-tion of the PLCP header 5 is/are used to set an identifier 4 therein which indicates the existence of postamble 3. The iden-tifier 4 can be a flag set in a single bit of the "Reserved SERVICE Bits" section of the PLCP header 5, as shown in Fig. 3 for bit 15, or a flag set in the single "Reserved 1 bit" fol-lowing the 4 RATE bits in the PLCP header 5. Alternatively, more than 1 bit could be used of the available (in total: 1 +
9) reserved bits of the PLOP header 5 to set a code therein
- 5 -(maximum code length: 1 + 9 = 10 bits), indicating the presence and preferably also coding a type of the postamble 3 used.
Extending the pilot pattern in this way has two ad-vantages: (i) the channel can be tracked accurately; (ii) the postamble 3 is transparent to older receivers since the latter stop receiving after the number of OFDM symbols indicated in the LENGTH field has been decoded; such older receivers will simply observe a channel that is occupied for one or more further symbol time(s).
In an improved receiver capable of using postamble 3 in addition to preamble 1, the reserved bit(s) in the header 5 is/are checked for the presence of the identifier 4 and, if such an identifier 4 is detected, postamble 3 is used in combi-nation with preamble 1 to estimate the channel.
Estimating the OFDM transmission channel by means of pre-and postambles 1, 3 is known in the art per se and e.g. dis-closed in S. Rossi and R.R. Muller, loc. cit., the disclosure of which is incorporated herein by reference. In particular, the channel estimation technique involves the use of a 2-dimensional interpolation - in time and frequency - between the preamble 1 and the postamble 3 by means of a Wiener Filter.
Fig. 4 shows the results of a comparison test of the new method of Fig. 3 and new pilot pattern of Fig. 2 as compared to a conventional channel estimation technique involving only pre-amble 1. Fig. 4 shows the bit error rate (BER) over signal-to-noise ratio (SNR) Eb/No for five different channel estimation methods all of which use discret prolate spheroidal (DPS) se-quences to model and estimate the channel. The first three curves labelled "llp DPS" refer to conventional channel estima-tion techniques with 1, 2, and 12 iterations of the Wiener Fil-ter, respectively. The last two curves labelled "lipPost DPS"
refer to two embodiments of the improved method including pre-and postambles 1, 3 with one and two iterations, respectively.
The comparison was made by means of an 802.11p link level simulator. As simulated environment, a NLOS channel with 400 ns
Extending the pilot pattern in this way has two ad-vantages: (i) the channel can be tracked accurately; (ii) the postamble 3 is transparent to older receivers since the latter stop receiving after the number of OFDM symbols indicated in the LENGTH field has been decoded; such older receivers will simply observe a channel that is occupied for one or more further symbol time(s).
In an improved receiver capable of using postamble 3 in addition to preamble 1, the reserved bit(s) in the header 5 is/are checked for the presence of the identifier 4 and, if such an identifier 4 is detected, postamble 3 is used in combi-nation with preamble 1 to estimate the channel.
Estimating the OFDM transmission channel by means of pre-and postambles 1, 3 is known in the art per se and e.g. dis-closed in S. Rossi and R.R. Muller, loc. cit., the disclosure of which is incorporated herein by reference. In particular, the channel estimation technique involves the use of a 2-dimensional interpolation - in time and frequency - between the preamble 1 and the postamble 3 by means of a Wiener Filter.
Fig. 4 shows the results of a comparison test of the new method of Fig. 3 and new pilot pattern of Fig. 2 as compared to a conventional channel estimation technique involving only pre-amble 1. Fig. 4 shows the bit error rate (BER) over signal-to-noise ratio (SNR) Eb/No for five different channel estimation methods all of which use discret prolate spheroidal (DPS) se-quences to model and estimate the channel. The first three curves labelled "llp DPS" refer to conventional channel estima-tion techniques with 1, 2, and 12 iterations of the Wiener Fil-ter, respectively. The last two curves labelled "lipPost DPS"
refer to two embodiments of the improved method including pre-and postambles 1, 3 with one and two iterations, respectively.
The comparison was made by means of an 802.11p link level simulator. As simulated environment, a NLOS channel with 400 ns
6 -maximum excess delay and a Doppler profile corresponding to a relative speed of 150 km/h was used. For the conventional pilot pattern of Fig. 1, the block length was 34 OFDM symbols corre-sponding to 200 bytes of QPSK modulated data with a code rate of . For the improved pilot pattern of Fig. 2, the block length was 35 OFDM symbols (because of the additional postamble 3) . The implemented receiver used the theorems of "Iterative soft channel estimation and detection" disclosed i.a. in T. Ze-men, C. F. Mecklenbrauker, J. Wehinger, and R.R. Muller, "Itera-tive joint time-variant channel estimation and multi-user de-tection for MC-CDMA", IEEE Trans. Wireless Commun., vol. 5, no.
6, pp. 1469-1478, June 2006; T. Zemen, H. Hofstetter, and G.
Steinbock, "Successive Slepian subspace projection in time and frequency for time-varaint channel estimation", in 14th IST Mo-bile and Wireless Communication Summit (IST SUMMIT), Dresden, Germany, June 19-22 2005; and S. Rossi and R.R. Muller, loc.
cit.; the disclosures of which are incorporated herein by ref-erence.
The simulations were performed over 100 frames. The con-ventional pilot pattern showed an error floor in BER for few (1 or 2) iterations. Only when increasing the number of iterations to a high number an acceptable receiver performance was achiev-able. In contrast thereto, for the improved channel estimation method, already the first iteration led to acceptable receiver performance, and two iterations corresponded to an optimum re-ceiver.
The invention is not limited to the specific embodiments enclosed herein but encompasses all variants and modifications thereof which are comprised by the enclosed claims.
6, pp. 1469-1478, June 2006; T. Zemen, H. Hofstetter, and G.
Steinbock, "Successive Slepian subspace projection in time and frequency for time-varaint channel estimation", in 14th IST Mo-bile and Wireless Communication Summit (IST SUMMIT), Dresden, Germany, June 19-22 2005; and S. Rossi and R.R. Muller, loc.
cit.; the disclosures of which are incorporated herein by ref-erence.
The simulations were performed over 100 frames. The con-ventional pilot pattern showed an error floor in BER for few (1 or 2) iterations. Only when increasing the number of iterations to a high number an acceptable receiver performance was achiev-able. In contrast thereto, for the improved channel estimation method, already the first iteration led to acceptable receiver performance, and two iterations corresponded to an optimum re-ceiver.
The invention is not limited to the specific embodiments enclosed herein but encompasses all variants and modifications thereof which are comprised by the enclosed claims.
Claims (5)
1. A method of channel estimation in an OFDM transmis-sion system having a transmitter and a receiver according to standard IEEE 802.11x, comprising:
in the transmitter, setting an identifier in the reserved bits section of the header following the preamble in a physical layer frame, attaching a postamble at the end of said frame without altering the length information in the header, and transmitting said frame over the channel, in the receiver, checking said reserved bits section in the header of a frame received over the channel for said iden-tifier and, if said identifier is detected, using the postamble and the preamble of the frame to estimate the channel.
in the transmitter, setting an identifier in the reserved bits section of the header following the preamble in a physical layer frame, attaching a postamble at the end of said frame without altering the length information in the header, and transmitting said frame over the channel, in the receiver, checking said reserved bits section in the header of a frame received over the channel for said iden-tifier and, if said identifier is detected, using the postamble and the preamble of the frame to estimate the channel.
2. The method of claim 1, wherein the channel is esti-mated by 2-dimensional interpolation in time and frequency be-tween the preamble and the postamble by means of a Wiener Fil-ter.
3. The method of claim 1 or 2, wherein said identifier is a flag in the reserved bit of the signal section of the header.
4. The method of claim 1 or 2, wherein said identifier is a code set in one or more of the reserved bits of the ser-vice bits section of the header.
5. The method of any of the claims 1 to 4, wherein said postamble is an OFDM symbol containing a known pilot pattern.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP10450186.1A EP2461530B9 (en) | 2010-12-02 | 2010-12-02 | Channel estimation in an OFDM transmission system |
| EP10450186.1 | 2010-12-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2753721A1 true CA2753721A1 (en) | 2012-06-02 |
| CA2753721C CA2753721C (en) | 2018-03-13 |
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| EP (1) | EP2461530B9 (en) |
| CN (1) | CN102487373A (en) |
| AU (1) | AU2011226905B2 (en) |
| CA (1) | CA2753721C (en) |
| CL (1) | CL2011003053A1 (en) |
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| US7248559B2 (en) | 2001-10-17 | 2007-07-24 | Nortel Networks Limited | Scattered pilot pattern and channel estimation method for MIMO-OFDM systems |
| EP2995016B1 (en) | 2013-05-09 | 2018-06-13 | Intel Corporation | Detection of 802.11p signals in 802.11n/ac enabled devices |
| US10491246B2 (en) * | 2013-08-29 | 2019-11-26 | Harman International Industries, Incorporated | Soft decision decoding method and system thereof |
| CN105594171B (en) * | 2013-09-30 | 2019-03-22 | 沃尔沃汽车公司 | Method for introducing supplementary training symbol in from the 802.11p OFDM frame to vehicle-carrying communication |
| US20160286011A1 (en) * | 2015-03-26 | 2016-09-29 | Assaf Kasher | Techniques for communicating an end of packet indicator |
| JP6672554B2 (en) * | 2018-05-22 | 2020-03-25 | アンリツ株式会社 | Measuring device and measuring method |
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| US7020166B2 (en) * | 2000-10-03 | 2006-03-28 | Broadcom Corporation | Switch transferring data using data encapsulation and decapsulation |
| US6978151B2 (en) * | 2001-05-10 | 2005-12-20 | Koninklijke Philips Electronics N.V. | Updating path loss estimation for power control and link adaptation in IEEE 802.11h WLAN |
| US7035294B2 (en) * | 2001-06-04 | 2006-04-25 | Calix Networks, Inc. | Backplane bus |
| US20020199021A1 (en) * | 2001-06-26 | 2002-12-26 | Niels Beier | Method and apparatus for using the type/length field in an ethernet mac header for carrying generic tags/labels |
| US7088702B2 (en) * | 2001-10-03 | 2006-08-08 | Freescale Semiconductor Inc. | Method for controlling a data stream in a wireless network |
| US6993039B2 (en) * | 2002-07-22 | 2006-01-31 | Utstarcom, Inc. | System and method for GRE heartbeats |
| KR100670423B1 (en) * | 2004-11-04 | 2007-01-16 | 삼성전자주식회사 | System and method for communication using heterogeneous neighbor base station information in a broadband wireless access communication system |
| US20070286107A1 (en) * | 2006-06-12 | 2007-12-13 | Harkirat Singh | System and method for wireless communication of uncompressed video having multiple destination aggregation (MDA) |
| US9225996B2 (en) * | 2007-12-19 | 2015-12-29 | Vixs Systems, Inc. | Motion refinement engine with flexible direction processing and methods for use therewith |
| US8355447B2 (en) * | 2007-12-19 | 2013-01-15 | Vixs Systems, Inc. | Video encoder with ring buffering of run-level pairs and methods for use therewith |
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| KR101520663B1 (en) * | 2008-02-03 | 2015-05-15 | 엘지전자 주식회사 | Preamble transmission method for legacy support |
| US20090209206A1 (en) | 2008-02-15 | 2009-08-20 | The Hong Kong University Of Science And Technology | Optimal mimo isi channel estimation using loosely synchronized codes and their variations |
| WO2011100583A2 (en) * | 2010-02-12 | 2011-08-18 | Yitran Communications Ltd. | Digital communication system for use in high noise channels |
| US20120082253A1 (en) * | 2010-07-12 | 2012-04-05 | Texas Instruments Incorporated | Pilot Structure for Coherent Modulation |
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2010
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- 2010-12-02 DK DK10450186.1T patent/DK2461530T3/en active
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-
2011
- 2011-09-27 AU AU2011226905A patent/AU2011226905B2/en active Active
- 2011-09-28 CA CA2753721A patent/CA2753721C/en active Active
- 2011-10-03 NZ NZ595527A patent/NZ595527A/en unknown
- 2011-10-24 ZA ZA2011/07775A patent/ZA201107775B/en unknown
- 2011-11-11 US US13/294,555 patent/US20120140835A1/en not_active Abandoned
- 2011-11-16 CN CN201110362373XA patent/CN102487373A/en active Pending
- 2011-12-01 RU RU2011149082/07A patent/RU2011149082A/en not_active Application Discontinuation
- 2011-12-02 CL CL2011003053A patent/CL2011003053A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| CL2011003053A1 (en) | 2012-10-12 |
| EP2461530B9 (en) | 2013-04-10 |
| PT2461530E (en) | 2012-12-26 |
| CN102487373A (en) | 2012-06-06 |
| EP2461530B1 (en) | 2012-10-10 |
| EP2461530A1 (en) | 2012-06-06 |
| CA2753721C (en) | 2018-03-13 |
| NZ595527A (en) | 2012-03-30 |
| ES2396019T3 (en) | 2013-02-18 |
| AU2011226905A1 (en) | 2012-06-21 |
| ZA201107775B (en) | 2012-07-25 |
| PL2461530T3 (en) | 2013-03-29 |
| AU2011226905B2 (en) | 2013-11-21 |
| DK2461530T3 (en) | 2013-01-28 |
| US20120140835A1 (en) | 2012-06-07 |
| SI2461530T1 (en) | 2013-01-31 |
| RU2011149082A (en) | 2013-06-10 |
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