Tuesday, December 30, 2008
W-CDMA Development
W-CDMA was developed by NTT Do Como as the air interface for their 3G network FOMA. Later NTT Do Como submitted the specification to the International Telecommunication Union (ITU) as a candidate for the international 3G standard known as IMT-2000. The ITU eventually accepted W-CDMA as part of the IMT-2000 family of 3G standards, as an alternative to CDMA2000, EDGE, and the short range DECT system. Later, W-CDMA was selected as the air interface for UMTS, the 3G successor to GSM.
Code Division Multiple Access communication networks have been developed by a number of companies over the years, but development of cell-phone networks based on CDMA (prior to W-CDMA) was dominated by Qualcomm, the first company to succeed in developing a practical and cost-effective CDMA implementation for consumer cell phones, its early IS-95 air interface standard. IS-95 evolved into the current CDMA2000 (IS-856/IS-2000) standard.
In the late 1990s, NTT Do Como began work on a new wide-band CDMA air interface for their planned 3G network FOMA. Foam’s air interface, called W-CDMA, was selected as the air interface for UMTS, a newer W-CDMA based system designed to be an easier upgrade for European GSM networks compared to FOMA. FOMA and UMTS use essentially the same air interface, but are different in other ways; thus, handsets are not 100% compatible between FOMA and UMTS, but roaming is supported.
Code Division Multiple Access communication networks have been developed by a number of companies over the years, but development of cell-phone networks based on CDMA (prior to W-CDMA) was dominated by Qualcomm, the first company to succeed in developing a practical and cost-effective CDMA implementation for consumer cell phones, its early IS-95 air interface standard. IS-95 evolved into the current CDMA2000 (IS-856/IS-2000) standard.
In the late 1990s, NTT Do Como began work on a new wide-band CDMA air interface for their planned 3G network FOMA. Foam’s air interface, called W-CDMA, was selected as the air interface for UMTS, a newer W-CDMA based system designed to be an easier upgrade for European GSM networks compared to FOMA. FOMA and UMTS use essentially the same air interface, but are different in other ways; thus, handsets are not 100% compatible between FOMA and UMTS, but roaming is supported.
Tuesday, December 23, 2008
W-CDMA Technical features
* Radio channels are 5MHz wide.
* Chip rate of 3.84 Mcps
* Supports two basic modes of duplex: frequency division and time division. Current systems use frequency division, one frequency for up link and one for down link. For time division, FOMA uses sixteen slots per radio frame, whereas UMTS uses fifteen slots per radio frame.
* Employs coherent detection on both the up link and down link based on the use of pilot symbols and channels.
* Supports inter-cell asynchronous operation.
* Variable mission on a 10 ms frame basis.
* Multi mode transmission.
* Adaptive power control based on SIR (Signal-to-Interference Ratio).
* Multi-user detection and smart antennas can be used to increase capacity and coverage.
* Multiple types of hand off (or handover) between different cells including soft hand off, softer hand off and hard hand off.
* Chip rate of 3.84 Mcps
* Supports two basic modes of duplex: frequency division and time division. Current systems use frequency division, one frequency for up link and one for down link. For time division, FOMA uses sixteen slots per radio frame, whereas UMTS uses fifteen slots per radio frame.
* Employs coherent detection on both the up link and down link based on the use of pilot symbols and channels.
* Supports inter-cell asynchronous operation.
* Variable mission on a 10 ms frame basis.
* Multi mode transmission.
* Adaptive power control based on SIR (Signal-to-Interference Ratio).
* Multi-user detection and smart antennas can be used to increase capacity and coverage.
* Multiple types of hand off (or handover) between different cells including soft hand off, softer hand off and hard hand off.
Tuesday, December 16, 2008
W-CDMA (UMTS)
W-CDMA (Wide band Code Division Multiple Access) is a type of 3G cellular network. W-CDMA is the higher speed transmission protocol used in the Japanese FOMA system and in the UMTS system, a third generation follow-on to the 2G GSM networks deployed worldwide.
W-CDMA is a wide band spread-spectrum mobile air interface that utilizes the direct-sequence spread spectrum method of asynchronous code division multiple access to achieve higher speeds and support more users compared to the implementation of time division multiplexing (TDMA) used by 2G GSM networks.
The term "W-CDMA" is also used to refer to the standard data interface used by the UMTS mobile communication system, W-CDMA (UMTS).
W-CDMA is a wide band spread-spectrum mobile air interface that utilizes the direct-sequence spread spectrum method of asynchronous code division multiple access to achieve higher speeds and support more users compared to the implementation of time division multiplexing (TDMA) used by 2G GSM networks.
The term "W-CDMA" is also used to refer to the standard data interface used by the UMTS mobile communication system, W-CDMA (UMTS).
Tuesday, December 09, 2008
HSDPA-High-Speed Down link Packet Access
High-Speed Down link Packet Access (HSDPA) is a 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA deployments support down-link speeds of 1.8, 3.6, 7.2 and 14.4 Mbit/s. Further speed increases are available with HSPA+, which provides speeds of up to 42 Mbit/s downlink.
The amount of the channelization code tree, and thus network bandwidth, allocated to HSDPA users is determined by the network. The allocation is "semi-static" in that it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation represents a trade-off between bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA data users. The allocation is in units of channelization codes for Spreading Factor 16, of which 16 exist and up to 15 can be allocated to HSDPA. When the base station decides which users will receive data on the next frame, it also decides which channelization codes will be used for each user.
This information is sent to the user devices over one or more HSDPA "scheduling channels"; these channels are not part of the HSDPA allocation previously mentioned, but are allocated separately. Thus, for a given 2 ms frame, data may be sent to a number of users simultaneously, using different channelization codes. The maximum number of users to receive data on a given 2 ms frame is determined by the number of allocated channelization codes.
The amount of the channelization code tree, and thus network bandwidth, allocated to HSDPA users is determined by the network. The allocation is "semi-static" in that it can be modified while the network is operating, but not on a frame-by-frame basis. This allocation represents a trade-off between bandwidth allocated for HSDPA users, versus that for voice and non-HSDPA data users. The allocation is in units of channelization codes for Spreading Factor 16, of which 16 exist and up to 15 can be allocated to HSDPA. When the base station decides which users will receive data on the next frame, it also decides which channelization codes will be used for each user.
This information is sent to the user devices over one or more HSDPA "scheduling channels"; these channels are not part of the HSDPA allocation previously mentioned, but are allocated separately. Thus, for a given 2 ms frame, data may be sent to a number of users simultaneously, using different channelization codes. The maximum number of users to receive data on a given 2 ms frame is determined by the number of allocated channelization codes.
