17-06-2014, 10:10 AM
HIGH SPEED DOWNLINK PACKET ACCESS
[attachment=64952]
ABSTRACT
Mobile wireless communications has already dramatically affected our lives, and will continue to do so as usage, services, and coverage rapidly expand with the adoption of the Third Generation of cellular wireless, and the transition to Internet-protocol based networks. Third Generation (3G) wireless, encompassing three forms of CDMA–CDMA2000 including 1X and EV-DO, WCDMA, also called UMTS and 3GSM. Both plug-in cards and integral modems are supporting broadband mobile communications directly to laptops. An abundance of powerful handsets are now reaching the market, which support a wide variety of services including music, streamed and stored video, multiplayer games, multiparty instant messaging, and location-based services. Such growth in usage and applications poses great challenges for the network operators, test equipment vendors, infrastructure manufacturers, and the technical staff that plan, deploy, and operate these networks. In this report let us focus on High-Speed Downlink Packet Access (HSDPA), a 3G performance enhancement protocol in mobile telephony communications.
INTRODUCTION:
High-Speed Downlink Packet Access (HSDPA) is an enhanced 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, also dubbed 3.5G, 3G+ or turbo 3G. Actually speaking it is
a 3G performance enhancement protocol and does not change the core network .It is a standard for radio interface in downlink direction. It allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity in downlink. It is the first part of High Speed Packet Access (HSPA) evolution and was introduced in Release 5 version. It evolved from Release 99/4 of WCDMA and backward is compatible with WCDMA systems in same frequency band of 5MHz
BASICS OF HSDPA :
3.a.UMTS:
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing Cdma One technology. UMTS uses wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators. UMTS specifies a complete network system which uses, covering the radio access network (UMTS Terrestrial Radio Access Network, or UTRAN), the core network (Mobile Application Part, or MAP) and the authentication of users via SIM (subscriber identity module cards).
The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access (FOMA) or 3GSM.
UMTS supports maximum theoretical data transfer rates of 42 Mbit/s when HSPA+ is implemented in the network. Users in deployed networks can expect a transfer rate of up to 384 kbit/s for Release '99 (R99) handsets (the original UMTS release), and 7.2 Mbit/s for HSDPA handsets in the downlink connection. These speeds are significantly faster than the 9.6 kbit/s of a single GSM error-corrected circuit switched data channel, multiple 9.6 kbit/s channels in HSCSD and 14.4 kbit/s for CDMAOne channels. Compared to the GSM reference network, the only difference is the introduction of the Radio Network Controller (RNC) and Node Bs within the newly formed Radio Network System (RNS). Essentially, these two nodes perform tasks equivalent to the BSC and BTS, respectively, in the GSM architecture
3.b.WCDMA:
W-CDMA (Wideband Code Division Multiple Access), UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface standard found in 3G mobile telecommunications networks. It is the most-commonly used member of the Universal Mobile Telecommunications System (UMTS) family. It uses the DS-CDMA channel access method and the FDD duplexing method to achieve higher speeds and support more users compared to most time division multiple access (TDMA) and time division duplex (TDD) schemes used before in UMTS. It uses the same core network as the 2G GSM networks deployed worldwide, allowing dual mode mobile operation along with GSM/EDGE; a feat it shares with other members of the UMTS family.
3.c. HSPA:
High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA protocols. A further improved 3GPP standard, Evolved HSPA (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 168 Mbit/s in the downlink and 22 Mbit/s in the uplink. The first HSPA specifications supported increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. It also reduced latency and provided up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink compared to original WCDMA protocols.
.RELEASE’99 WCDMA DOWNLINK PACKET DATA CAPABILITIES:
Channels in Release’99/ Release’4 WCDMA specifications that can be used for downlink packet data are :
Dedicated Channel (DCH)
• Used for any type of service
• Fixed spreading factor (SF) in downlink (it reserves the code space capacity according to the peak data rate for connection). This can be used even up to 2Mbps, but reversing the code tree a very high peak rate with low actual duty cycle is not a very efficient use of code resources
• Power-controlled and may be operated in soft handover.
Downlink-shared Channel(DSCH)
• Operates always together with a DCH. This way, channel properties can be defined to best suit packet data needs while leaving the data with tight delay budget such as speech or video ,to be carried by the DCH
• Dynamically varying SF informed on a 10-ms frame -by-frame basis with the Transport Format Combination Indicator(TFCI) signaling carried on the associated DCH.
• The DSCH code resources can be shared between several users and the channel may employ either single or multi code transmission
• Fast power controlled with the associated DCH but does not support soft handover for example ,speech is proved on DCH if present with packet data
HYBRID –AUTOMATIC REPEAT REQUEST (H-ARQ)
Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of high-rate forward error-correcting coding and ARQ error-control. In standard ARQ, redundant bits are added to data to be transmitted using an error-detecting (ED) code such as a cyclic redundancy check (CRC). Receivers detecting a corrupted message will request a new message from the sender. In Hybrid ARQ, the original data is encoded with a forward error correction (FEC) code, and the parity bits are either immediately sent along with the message or only transmitted upon request when a receiver detects an erroneous message. The ED code may be omitted when a code is used that can perform both forward error correction (FEC) in addition to error detection, such as a Reed-Solomon code. The FEC code is chosen to correct an expected subset of all errors that may occur, while the ARQ method is used as a fall-back to correct errors that are uncorrectable using only the redundancy sent in the initial transmission. As a result, hybrid ARQ performs better than ordinary ARQ in poor signal conditions, but in its simplest form this comes at the expense of significantly lower throughput in good signal conditions. There is typically a signal quality cross-over point below which simple hybrid ARQ is better, and above which basic ARQ is better.
HIGH – SPEED SHARED CONTROL CHANNEL (HS-SCCH)
HS-SCCH carries the key information necessary for HS-DSCH demodulation
The UTRAN needs to allocate a number of HS-SCCHs that correspond to the maximum number of users that will be code-multiplexed
Each terminal will only need to consider a maximum of 4 HS-SCCHs at a given time. The HS-SCCHs that are to be considered are signaled to terminals by the network
Each HS-SCCH block has a three-slot duration that is divided into two functional parts
• The HS-SCCH Part 1:The first slot carries the time-critical information that is needed to start the demodulation process in due time to avoid chip level buffering
Code to despread .This also relates to the terminal capability in which each terminal category indicates whether the current terminal can despread a maximum of 5,10 or 15 codes
Modulation to indicate if QPSK or 16-QAM is used
• The HS-SCCH Part 2:The next two slots contain less time-critical parameters including Cyclic Redundancy Check(CRC) to check the validity of the HS-SCCH information and HARQ process information
Redundancy version information to allow proper decoding and combining with the possible earlier transmission
ARQ process number to show which ARQ process the data belongs to
First transmission or retransmission indicator to indicate whether the transmission is to be combined with the existing data in the buffer (if not successfully decoded earlier )or whether the buffer should be flushed and filled with new data
• For protection, both HS-SCCH parts employ terminal-specific masking to allow the terminal to decide whether the detected control channel is actually intended for the particular terminal
• Parameters such as actual channel coding rate are not signaled but can be derived from the transport format parameters
The HS-SCCH uses SF 128 that can accommodate 40 bits per slot (after channel encoding) because there are no pilot or Transmit Power Control(TPC) bits on HS-SCCH
23 CONCLUSION:
High Speed Downlink Packet Access (HSPDA) is a concept within WCDMA specifications whose main target is to increase user peak data rates and quality of service, and to generally improve spectral efficiency for downlink asymmetrical and bursty packet data services. It is designed to increase packet throughput by means of fast physical layer (L1) retransmission and transmission combining as well as link adaptation
[attachment=64952]
ABSTRACT
Mobile wireless communications has already dramatically affected our lives, and will continue to do so as usage, services, and coverage rapidly expand with the adoption of the Third Generation of cellular wireless, and the transition to Internet-protocol based networks. Third Generation (3G) wireless, encompassing three forms of CDMA–CDMA2000 including 1X and EV-DO, WCDMA, also called UMTS and 3GSM. Both plug-in cards and integral modems are supporting broadband mobile communications directly to laptops. An abundance of powerful handsets are now reaching the market, which support a wide variety of services including music, streamed and stored video, multiplayer games, multiparty instant messaging, and location-based services. Such growth in usage and applications poses great challenges for the network operators, test equipment vendors, infrastructure manufacturers, and the technical staff that plan, deploy, and operate these networks. In this report let us focus on High-Speed Downlink Packet Access (HSDPA), a 3G performance enhancement protocol in mobile telephony communications.
INTRODUCTION:
High-Speed Downlink Packet Access (HSDPA) is an enhanced 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, also dubbed 3.5G, 3G+ or turbo 3G. Actually speaking it is
a 3G performance enhancement protocol and does not change the core network .It is a standard for radio interface in downlink direction. It allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity in downlink. It is the first part of High Speed Packet Access (HSPA) evolution and was introduced in Release 5 version. It evolved from Release 99/4 of WCDMA and backward is compatible with WCDMA systems in same frequency band of 5MHz
BASICS OF HSDPA :
3.a.UMTS:
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing Cdma One technology. UMTS uses wideband code division multiple access (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators. UMTS specifies a complete network system which uses, covering the radio access network (UMTS Terrestrial Radio Access Network, or UTRAN), the core network (Mobile Application Part, or MAP) and the authentication of users via SIM (subscriber identity module cards).
The technology described in UMTS is sometimes also referred to as Freedom of Mobile Multimedia Access (FOMA) or 3GSM.
UMTS supports maximum theoretical data transfer rates of 42 Mbit/s when HSPA+ is implemented in the network. Users in deployed networks can expect a transfer rate of up to 384 kbit/s for Release '99 (R99) handsets (the original UMTS release), and 7.2 Mbit/s for HSDPA handsets in the downlink connection. These speeds are significantly faster than the 9.6 kbit/s of a single GSM error-corrected circuit switched data channel, multiple 9.6 kbit/s channels in HSCSD and 14.4 kbit/s for CDMAOne channels. Compared to the GSM reference network, the only difference is the introduction of the Radio Network Controller (RNC) and Node Bs within the newly formed Radio Network System (RNS). Essentially, these two nodes perform tasks equivalent to the BSC and BTS, respectively, in the GSM architecture
3.b.WCDMA:
W-CDMA (Wideband Code Division Multiple Access), UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface standard found in 3G mobile telecommunications networks. It is the most-commonly used member of the Universal Mobile Telecommunications System (UMTS) family. It uses the DS-CDMA channel access method and the FDD duplexing method to achieve higher speeds and support more users compared to most time division multiple access (TDMA) and time division duplex (TDD) schemes used before in UMTS. It uses the same core network as the 2G GSM networks deployed worldwide, allowing dual mode mobile operation along with GSM/EDGE; a feat it shares with other members of the UMTS family.
3.c. HSPA:
High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA protocols. A further improved 3GPP standard, Evolved HSPA (also known as HSPA+), was released late in 2008 with subsequent worldwide adoption beginning in 2010. The newer standard allows bit-rates to reach as high as 168 Mbit/s in the downlink and 22 Mbit/s in the uplink. The first HSPA specifications supported increased peak data rates of up to 14 Mbit/s in the downlink and 5.76 Mbit/s in the uplink. It also reduced latency and provided up to five times more system capacity in the downlink and up to twice as much system capacity in the uplink compared to original WCDMA protocols.
.RELEASE’99 WCDMA DOWNLINK PACKET DATA CAPABILITIES:
Channels in Release’99/ Release’4 WCDMA specifications that can be used for downlink packet data are :
Dedicated Channel (DCH)
• Used for any type of service
• Fixed spreading factor (SF) in downlink (it reserves the code space capacity according to the peak data rate for connection). This can be used even up to 2Mbps, but reversing the code tree a very high peak rate with low actual duty cycle is not a very efficient use of code resources
• Power-controlled and may be operated in soft handover.
Downlink-shared Channel(DSCH)
• Operates always together with a DCH. This way, channel properties can be defined to best suit packet data needs while leaving the data with tight delay budget such as speech or video ,to be carried by the DCH
• Dynamically varying SF informed on a 10-ms frame -by-frame basis with the Transport Format Combination Indicator(TFCI) signaling carried on the associated DCH.
• The DSCH code resources can be shared between several users and the channel may employ either single or multi code transmission
• Fast power controlled with the associated DCH but does not support soft handover for example ,speech is proved on DCH if present with packet data
HYBRID –AUTOMATIC REPEAT REQUEST (H-ARQ)
Hybrid automatic repeat request (hybrid ARQ or HARQ) is a combination of high-rate forward error-correcting coding and ARQ error-control. In standard ARQ, redundant bits are added to data to be transmitted using an error-detecting (ED) code such as a cyclic redundancy check (CRC). Receivers detecting a corrupted message will request a new message from the sender. In Hybrid ARQ, the original data is encoded with a forward error correction (FEC) code, and the parity bits are either immediately sent along with the message or only transmitted upon request when a receiver detects an erroneous message. The ED code may be omitted when a code is used that can perform both forward error correction (FEC) in addition to error detection, such as a Reed-Solomon code. The FEC code is chosen to correct an expected subset of all errors that may occur, while the ARQ method is used as a fall-back to correct errors that are uncorrectable using only the redundancy sent in the initial transmission. As a result, hybrid ARQ performs better than ordinary ARQ in poor signal conditions, but in its simplest form this comes at the expense of significantly lower throughput in good signal conditions. There is typically a signal quality cross-over point below which simple hybrid ARQ is better, and above which basic ARQ is better.
HIGH – SPEED SHARED CONTROL CHANNEL (HS-SCCH)
HS-SCCH carries the key information necessary for HS-DSCH demodulation
The UTRAN needs to allocate a number of HS-SCCHs that correspond to the maximum number of users that will be code-multiplexed
Each terminal will only need to consider a maximum of 4 HS-SCCHs at a given time. The HS-SCCHs that are to be considered are signaled to terminals by the network
Each HS-SCCH block has a three-slot duration that is divided into two functional parts
• The HS-SCCH Part 1:The first slot carries the time-critical information that is needed to start the demodulation process in due time to avoid chip level buffering
Code to despread .This also relates to the terminal capability in which each terminal category indicates whether the current terminal can despread a maximum of 5,10 or 15 codes
Modulation to indicate if QPSK or 16-QAM is used
• The HS-SCCH Part 2:The next two slots contain less time-critical parameters including Cyclic Redundancy Check(CRC) to check the validity of the HS-SCCH information and HARQ process information
Redundancy version information to allow proper decoding and combining with the possible earlier transmission
ARQ process number to show which ARQ process the data belongs to
First transmission or retransmission indicator to indicate whether the transmission is to be combined with the existing data in the buffer (if not successfully decoded earlier )or whether the buffer should be flushed and filled with new data
• For protection, both HS-SCCH parts employ terminal-specific masking to allow the terminal to decide whether the detected control channel is actually intended for the particular terminal
• Parameters such as actual channel coding rate are not signaled but can be derived from the transport format parameters
The HS-SCCH uses SF 128 that can accommodate 40 bits per slot (after channel encoding) because there are no pilot or Transmit Power Control(TPC) bits on HS-SCCH
23 CONCLUSION:
High Speed Downlink Packet Access (HSPDA) is a concept within WCDMA specifications whose main target is to increase user peak data rates and quality of service, and to generally improve spectral efficiency for downlink asymmetrical and bursty packet data services. It is designed to increase packet throughput by means of fast physical layer (L1) retransmission and transmission combining as well as link adaptation