Technologies and Standards for TD-SCDMA Evolutions to IMT-Advanced

Picture Source: http://www.itu.int/dms_pub/itu-t/oth/21/05/T21050000010003PDFE.pdf

This is a summary of a paper from IEEE Communications Magazine, Dec 2009 issue titled "Technologies and Standards for TD-SCDMA Evolutions to IMT-Advanced" by Mugen Peng and Wenbo Wang of Beijing University of Posts and Telecommunications with my own comments and understanding.

As I have blogged about in the past that China Mobile has launched TD-SCDMA network in China and the main focus to to iron out the basic problems before moving onto the evolved TD-SCDMA network. Couple of device manufacturers have already started working on the TD-HSPA devices. Couple of months back, 3G Americas published a whitepaper giving overview and emphasising the advantages of TDD flavour of LTE as compared to FDD. The next milestone is the IMT-Advanced that is under discussion at the moment and China has already proposed TD-LTE-Advanced which would be compatible with the TD-SCDMA technology.

For anyone who does not know the difference between TDD, FDD and TD-SCDMA please see this blog.

The TD-SCDMA technology has been standardised quite a while back but the rollout has been slow. The commercial TD-SCDMA network was rolled out in 2009 and more and more device manufacturers are getting interested in the technology. This could be due to the fact that China Mobile has a customer base of over 500 million subscribers. As of July 2009 over 100 device manufacturers were working on TD-SCDMA technology.

The big problem with TD-SCDMA (as in the case of R99 3G) is that the practical data rate is 350kbps max. This can definitely not provide a broadband experience. To increase the data rates there are two different approaches. First is the Short Term Evolution (STE) and the other is Long Term Evolution (LTE).

The first phase of evolution as can be seen in the picture above is the TD-STE. This consists of single carrier and multi-carrier TD-HSDPA/TD-HSUPA (TD-HSPA), TD-MBMS and TD-HSPA+.

The LTE part is known as TD-LTE. There is a definite evolution path specified from TD-SCDMA to TD-LTE and hence TD-LTE is widely supported by the TD-SCDMA technology device manufacturers and operators. The target of TD-LTE is to enhance the capabilities of coverage, service provision, and mobility support of TD-SCDMA. To save investment and make full use of the network infrastructure available, the design of TD-LTE takes into account the features of TD-SCDMA, and keeps TD-LTE backward compatible with TD-SCDMA and TD-STE systems to ensure smooth migration.

The final phase of evolution is the 4G technology or IMT-Advanced and the TD-SCDMA candidate for TD-LTE+ is TD-LTE-Advanced. Some mature techniques related to the TD-SCDMA characteristics, such as beamforming (BF), dynamic channel allocation, and uplink synchronization, will be creatively incorporated in the TD-LTE+ system.

Some academic proposals were also made like the one available here on the future evolution of TD-SCDMA but they lacked the industry requirements and are just useful for theoretical research.

The standards of TD-SCDMA and its evolution systems are supervised by 3GPP in Europe and by CCSA (Chinese Cellular Standards Association) in China. In March 2001 3GPP fulfilled TD-SCDMA low chip rate (LCR) standardization in Release 4 (R4). The improved R4 and Release 5 (R5) specifications have added some promising functions including HSDPA, synchronization procedures, terminal location (angle of arrival [AOA]-aided location), and so on.

When the industry standardizations supervised by CCSA are focusing on the integration of R4 and R5, the N-frequency TD-SCDMA and the extension of HSDPA from single- to multicarrier are presented. Meanwhile, some networking techniques, such as N-frequency, polarized smart antenna, and a new networking configuration with baseband unit plus remote radio unit (BBU+RRU), are present in the commercial application of TD-SCDMA.

TD-SCDMA STE

For the first evolution phase of TD-SCDMA, three alternative solutions are considered. The first one is compatible with WCDMA STE, which is based on HSDPA/HSUPA technology. The second is to provide MBMS service via the compatible multicast broadcast single-frequency network (MBSFN) technique or the new union time-slot network (UTN) technique. The last is HSPA+ to achieve similar performance as LTE.

On a single carrier, TD-HSDPA can reach a peak rate of 2.8 Mb/s for each carrier when the

ratio of upstream and downstream time slots is 1:5. The theoretical peak transmission rate of a three-carrier HSDPA system with 16-quadrature amplitude modulation (QAM) is up to 8.4 Mb/s.

Single-carrier TD-HSUPA can achieve different throughput rates if the configurations and parameters are varied, including the number of occupied time slots, the modulation, and the transport block size in bytes. Considering the complexity of a terminal with several carriers in TD-HSUPA, multicarrier is configured in the Node B, while only one carrier is employed in the terminal.

In Rel-7 based TD-HSPA+, In order to match the performance of orthogonal frequency-division multiple access (OFDMA)-based TD-LTE systems, some advanced techniques are utilized, such as multiple-input multiple-output (MIMO), polarized BF, higher modulation and coding schemes (64-QAM is available), adaptive fast scheduling, multicarrier techniques, and so on. Theoretically, 64-QAM can improve performance by a factor of 1.5 compared to the current 16-QAM; for single-carrier the peak rate reaches 4.2 Mb/s, and three-carrier up to 12.6 Mb/s.

For the MIMO technique, double transmit antenna array (D-TxAA), based on the pre-coding method at the transmitter, has been employed in frequency-division duplex (FDD)-HSPA+ systems, while selective per antenna rate control (S-PARC), motivated by the Shannon capacity limit for an open loop MIMO link, has been applied in TD-HSPA+ systems.

TD-SCDMA LTE

The TD-SCDMA LTE program was kicked off in November 2004, and the LTE demand report was approved in June 2005. The LTE specified for TD_SCDMA evolution is named TD-LTE.

LTE systems are supposed to work in both FDD and TDD modes. LTE TDD and FDD modes have been greatly harmonized in the sense that both modes share the same underlying framework, including radio access schemes OFDMA in downlink and SC-FDMA in uplink, basic subframe formats, configuration protocols, and so on.

TD-LTE trials have already started last year with some positive results.

TD-SCDMA LTE+

IMT-Advanced can be regarded as a B3G/4G standard, and the current TD-SCDMA standard migrating to IMT-Advanced can be regarded as a thorough revolution. TD-LTE advanced (TD-LTE+) is a good match with the TD-SCDMA revolution to IMT-Advanced.

It is predicted that the future TD-SCDMA revolution technology will support data rates up to approximately 100 Mb/s for high mobility and up to approximately 1 Gb/s for low mobility such as nomadic/local wireless access.

Recently, some advanced techniques have been presented for TD-LTE+ in China, ranging from the system architecture to the radio processing techniques, such as multi-user (MU)-BF, wireless relaying, and carrier aggregation (CA).

For MU-BF see the paper proposed by Huawei, CHina Mobile and CATT here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_55b/Docs/R1-090133.zip).

For Wireless Relaying see the ZTE paper here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_56b/Docs/R1-091423.zip).

To achieve higher performance and target peak data rates, LTE+ systems should support bandwidth greater than 20 MHz (e.g., up to 100 MHz). Consequently, the requirements for TD-LTE+ include support for larger transmission bandwidths than in TD-LTE. Moreover, there should be backward compatibility so that a TD-LTE user can work in TD-LTE+ networks. CA is a concept that can provide bandwidth scalability while maintaining backward compatibility with TD-LTE through any of the constituent carriers, where multiple component carriers are aggregated to the desired TD-LTE+ system bandwidth. A TD-LTE R8 terminal can receive one of these component carriers, while an TD-LTE+ terminal can simultaneously access multiple component carriers. Compared to other approaches, CA does not require extensive changes to the TD-LTE physical layer structure and simplifies reuse of existing implementations. For more on Carrier Aggregation see CATT, LGE and Motorola paper here (http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_56b/Docs/R1-091655.zip).

Finally, there are some interesting developments happening in the TD-SCDMA market with bigger players getting interested. Once a critical mass is reached in the number of subscribers as well as the manufacturers I wouldnt be surprised if this technology is exported beyond the Chinese borders. With clear and defined evolution path this could be a win-win situation for everyone.

12 megapixel Sony Ericsson Satio coming next month

What can you do with a 12 megapixel camera in the phone? I for sure would be doing 'Megapixel Microscopy' and probably click 4-5 photos in a year.

Sony Ericsson recently announced Satio which provides you access to all your media in one place – just tap directly into your favourite features with the five standby panels and you’re ready to go. First introduced in Barcelona as the ‘Idou’, Satio puts the future of mobile entertainment in the palm of your hand. You can watch your favourite movies on the bus or catch up with your TV shows while on your lunch break thanks to Satio.

“With Satio you can enjoy any form of entertainment anytime, anywhere. Whether its music or movies you will never be more than a tap away from your favourite tracks or shows,” said Fredrik Mansson, Market Business Manager at Sony Ericsson. “Just tap directly into your favourite videos and music with the unique full touch media menu, standby panels and music player. Snapping perfect pictures also just got so simple thanks to the 12.1 megapixel camera, intuitive touch focus and Xenon flash. Share them with your nearest and dearest via your social networking site, produce huge prints and you can even comment directly on your images.”

Download exciting music, movies and games from PlayNow™ arena to personalise your entertainment experience on Satio and enjoy them in crystal clear 16:9 widescreen format. PlayNow™ arena provides a full range of mobile entertainment available by dual download to both your PC and mobile phone with specially developed ring tones and music tones and DRM-free music tracks and TrackID™ charts from around the world.

The Phone has 7.2Mbps HSDPA and 3.6Mbps HSUPA capability. There is a different model for US, China and the rest of the world. Thankfully it comes with 8GB SD card so you wont have to worry about transferring your images after every 10-15 photos.

The phone is going to be available in Sep 09 in UK and probably elsewhere.

Orthogonality and non orthogonality

Multiple access (MA) is a basic function in wireless cellular systems. Generally speaking, MA techniques can be classified into orthogonal and non-orthogonal approaches. In orthogonal approaches, signals from different users are orthogonal to each other, i.e., their cross correlation is zero, which can be achieved by time division multiple-access (TDMA), frequency-division multiple-access (FDMA) and orthogonal-frequency division multiple-access (OFDMA). Non-orthogonal schemes allow non-zero cross correlation among the signals from different users, such as in random waveform code-division multiple-access (CDMA), trellis-coded multiple-access (TCMA) and interleave-division multiple-access (IDMA).

First and second generation cellular systems are dominated by orthogonal MA approaches. The main advantage of these approaches is the avoidance of intra-cell interference. However, careful cell planning is necessary in these systems to curtail cross-cell interference. In particular, sufficient distance must exist between re-used channels, resulting in reduced cellular spectral efficiency.

Non-orthogonal CDMA techniques have been adopted in second and third generation cellular systems (e.g. CDMA2000 and uplink WCDMA). Compared with its orthogonal counterparts, CDMA is more robust against fading and cross-cell interference, but is prone to intracell interference. Due to its spread-spectrum nature, CDMA is inconvenient for data services (e.g., wireless local area networks (WLANs) and 3GPP high speed uplink/downlink packet access (HSUPA/HSDPA) standard) that require high single-user rates.

Communication services can be classified into delay sensitive and insensitive ones. A typical example of a delay-insensitive service is email. Typical examples of delay-sensitive services include speech and video applications. For delay insensitive services, rate constraints are relatively relaxed for individual users and maximizing the throughput by orthogonal methods is a common strategy. The maximum throughput can be achieved by a one-user transmission policy, where only the user with the largest channel gain is allowed to transmit. This implies time domain orthogonality as adopted in many WLANs. For delay-sensitive services, on the other hand, each user must transmit a certain amount of information within a certain period and maximizing the throughput is no longer an appropriate strategy. Rate constraints must be considered in this case.

CDMA is the most well known non-orthogonal technique. The main advantages of CDMA are its robustness against fading and cross-cell interference, and its flexibility in asynchronous transmission environments.

An uplink data transfer mechanism in the HSUPA is provided by physical HSUPA channels, such as an Enhanced Dedicated Physical Data Channel (E-DPDCH), implemented on top of Wideband Code Division Multiple Access (WCDMA) uplink physical data channels such as a Dedicated Physical Control Channel (DPCCH) and a Dedicated Physical Data Channel (DPDCH), thus sharing radio resources, such as power resources, with the WCDMA uplink physical data channels. The sharing of the radio resources results in inflexibility in radio resource allocation to the physical HSUPA channels and the WCDMA physical data channels. In CDMA, which is a non-orthogonal multiple access scheme, the signals from different users within the same cell interfere with one another. This type of interference is known as the intra-cell interference. In addition, the base station also receives the interference from the users transmitting in neighbouring cells. This is known as the inter-cell interference.

Uplink power control is typically intended to control the received signal power from the active user equipments (UEs) to the base as well as the rise-over-thermal (RoT), which is a measure of the total interference (intra- and inter-cell) relative to the thermal noise. In systems such as HSUPA, fast power control is required due to the fast fluctuation in multi-user (intra-cell) interference. This fast fluctuation will otherwise result in the well-known near-far problem. Moreover, as uplink transmission in an HSUPA system is not orthogonal, the signal from each transmitting UE is subject to interference from another transmitting UE. If the signal strength of UEs varies substantially, a stronger UE (for example, a UE in favourable channel conditions experiencing a power boost due to constructive short term channel fading such as Rayleigh fading) may completely overwhelm the signal of a weaker UE (with signal experiencing attenuation due to short term fading). To mitigate this problem, fast power control has been considered previously in the art where fast power control commands are transmitted from a base station to each UE to set the power of uplink transmission.

When an orthogonal multiple access scheme such as Single-Carrier Frequency Division Multiple Access (SC-FDMA), which includes interleaved and localized Frequency Division Multiple Access (FDMA) or Orthogonal Frequency Division Multiple Access (OFDMA), is used, multi-user interference is not present for low mobility and small for moderate mobility. This is the case for the next generation UMTS i.e. LTE system. LTE system employs SC-FDMA in uplink and OFDMA in downlink. As a result in the case of LTE, the fluctuation in the total interference only comes from inter-cell interference and thermal noise which tends to be slower. While fast power control can be utilized, it can be argued that its advantage is minimal. Hence, only slow power control is needed for orthogonal multiple access schemes.

Fundamental difference between HSDPA and HSUPA

It has been long time since HSDPA and HSUPA came into existence. Untill now we have read and implemented many features related to HSDPA and HSUPA. However following are the basic difference between HSDPA and HSUPA:

• In the downlink, the shared resource is transmission power and the code space, both of which are located in one central node, the NodeB. In the uplink, the shared resource is the amount of allowed uplink interference, which depends on the transmission power of multiple distributed nodes, the UEs.
• The scheduler and the transmission buffers are located in the same node in the downlink, while in the uplink the scheduler is located in the NodeB while the data buffers are distributed in the UEs. Hence, the UEs need to signal buffer status information to the scheduler.
• The WCDMA uplink, also with Enhanced Uplink, is inherently non-orthogonal, and subject to interference between uplink transmissions within the same cell. This is in contrast to the downlink, where different transmitted channels are orthogonal. Fast power control is therefore essential for the uplink to handle the near-far problem. The E-DCH is transmitted with a power offset relative to the power-controlled uplink control channel and by adjusting the maximum allowed power offset, the scheduler can control the E-DCH data rate. This is in contrast to HSDPA, where a (more or less) constant transmission power with rate adaptation is used.
• Soft handover is supported by the E-DCH. Receiving data from a terminal in multiple cells is fundamentally beneficial as it provides diversity, while transmission from multiple cells in case of HSDPA is cumbersome and with questionable benefits as discussed in the previous chapter. Soft handover also implies power control by multiple cells, which is necessary to limit the amount of interference generated in neighbouring cells and to maintain backward compatibility and coexistence with UE not using the E-DCH for data transmission.
• In the downlink, higher-order modulation, which trades power efficiency for bandwidth efficiency, is useful to provide high data rates in some situations, for example when the scheduler has assigned a small number of channelization codes for a transmission but the amount of available transmission power is relatively high. The situation in the uplink is different; there is no need to share channelization codes between users and the channel coding rates are therefore typically lower than for the downlink. Hence, unlike the downlink, higher order modulation is less useful in the uplink macro-cells and therefore not part of the first release of enhanced uplink.

Dual-Cell HSPA in Release 8 and beyond

Some interesting developments are ongoing in the 3GPP standardisation from Release-8 onwards. You must be aware that the current bandwidth in UMTS/HSPA is 5 MHz. Since most of the operators generally won bigger chunk of spectrum of contiguous 5MHz band, they can actually combine these chunks to create a larger spectrum and hence increase data rates.

In Release 8 in downlink, it is possible to increase data rates using either a combination of MIMO and 64QAM or dual-cell HSDPA for operation on two 5MHz carriers with 64QAM, data rates reach up to 42Mbps.

In deployments where multiple downlink carriers are available, the new multicarrier operation offers an attractive way of increasing coverage for high bit rates. Rel-8 introduces dual-carrier operation in the downlink on adjacent carriers. This technique doubles the peak rate from 21Mbps to 42Mbps without the use of MIMO – it doubles the rate for users with typical bursty traffic; therefore, it also doubles the average user throughput, which translates into a substantial increase in cell capacity.

You may remember that I mentioned earlier that the operators are not too keen on going for MIMO for non-LTE technology. This is because they will have to upgrade their hardware and the antennas which could increase their cost significantly for a technology that is not going to be around for long.

Another thing to note before it becomes too confusing is that there are two terms for 'DC' being used right now. One of them is 'Dual Carrier' and other is 'Dual Cell'. In Release 8, the term being used is Dual-Cell for HSDPA which is also known as DC-HSDPA. The Technical specification to follow is 3GPP, TR 25.825 “Dual-Cell HSDPA operation” V1.0.0, May 2008.

The Dual-Cell assumes that both the 5MHz bands are contiguous. If they are not then the better term to refer for DC is Dual-Carrier.

A dual-carrier user can be scheduled in the primary serving cell as well as in a secondary serving cell over two parallel HS-DSCH transport channels. All non-HSDPA-related channels reside in the primary serving cell, and all physical layer procedures are essentially based on the primary serving cell. Either carrier can be configured to function as the primary serving cell for a particular user. As a consequence, the dual-carrier feature also facilitates an efficient load balancing between carriers in one sector. As with MIMO, the two transport channels perform hybrid automatic repeat request (HARQ) retransmissions, coding and modulation independently. A difference compared to MIMO is that the two transport blocks can be transmitted on their respective carriers using a different number of channelization codes. In terms of complexity, adding a dual-carrier receiver to UEs is roughly comparable to adding a MIMO receiver. Because the two 5MHz carriers are adjacent, they can be received using a single 10MHz radio receiver, which is already be available if the UE is LTE-capable.

Following the introduction in Release 8 of dual-carrier operation in the downlink, 3GPP is now discussing operation on multiple 5MHz carriers. Multiband operation of multiple carriers allows a single user to simultaneously aggregate and use the spectrum distributed over different bands. This gives operators greater fl exibility when using available spectrum. Increasing the number of carriers that UEs receive from two to four doubles the peak rate and achievable user throughput. For bursty traffic, this translates into substantially greater capacity, either as a larger number of users at a given data rate, or as a higher data rate for a given number of users. To substantially boost spectral effi ciency, 3GPP is studying the combination of dual-carrier operation and MIMO with 64QAM in the downlink, thereby doubling the peak data rate to 84Mbps. Similarly, they are studying the combination of MIMO, 64QAM and up to four downlink carriers to support peak data rates of more than 100Mbps. The support for UE reception on two frequency bands is an enabler to DC-HSDPA for operators who do not have adjacent 5MHz carriers available in one band, and is therefore of key importance for the further evolution of multi carrier HSPA.

As a consequence of increased data rates in downlink, the uplink data rates need to be improved too. From the aggregation of multiple FDD downlink carriers, the paired FDD uplink carriers can be utilized for improved uplink transmissions. 3GPP studies the usage of two adjacent 5MHz carriers for dual carrier uplink transmissions (DC-HSUPA) supporting data rates of up to 23Mbps. A further benefit of utilizing two uplink carriers is the possibility to support more efficient load balancing in the uplink direction.

In summary, uplink multicarrier operation increases availability as well as coverage of high data rates in the uplink.

In Conclusion, Rel-8 defines improvements in HSPA to achieve higher rates through dual carrier or combined 64QAM+MIMO operation. With the Rel-8 specification nearing completion (targeted for March 2009), planning is already under way in 3GPP for Rel-9 and Rel-10. Further multi-carrier and MIMO options are being explored for HSPA in Rel-9 and Rel-10

If you want to explore this topic further see:

• Nomor research White Paper – Dual Cell HSDPA and its Future Evolution.
• WirelessMoves - Dual Carrier HSDPA - The Push Beyond 5 MHz
• Ericsson - Continued HSPA Evolution of mobile broadband

HSUPA is here

T-Mobile recently launched HSUPA network here in UK:

T-Mobile said, in certain areas, upload speeds will be five times faster than previously. It claims upload speeds of up to 1.4 Mbps. T-Mobile UK chief executive Jim Hyde said: "Mobile broadband has come of age. Today, 25 per cent of new contract customers are signing up and we expect to quadruple our user base in 2008.

"We knew mobile broadband would burst on to the scene and our continued investment in new technology is paying dividends for customers seeking a fast, consistent service which offers great value."

T-Mobile has also upgraded its HSDPA network, it said. It now boasts download speeds of up to 7.2Mbps within the M25.

Meanwhile, T-Mobile Germany has annoucned the completion of the HSPA upgrade to it's 3G network, meaning that customers can now download (HSDPA) at 7.2Mbps. The plan is that the upload speed (HSUPA) will be boosted to 2Mbps by the end of the year.

In other news, AT&T in USA plans for 2008 include the completion of the nation's first High Speed Uplink Packet Access (HSUPA)-enabled network by the middle of the year. The AT&T 3G network now delivers typical downlink speeds ranging between 700 Kbps (kilobits per second) and 1.7 Mbps (megabits per second), and it will now offer faster uplink speeds ranging between 500 Kbps and 1.2 Mbps. The faster uplink speeds allow AT&T's HSUPA-enabled laptop users to quickly send large files and take full advantage of the latest Internet and business applications.

An article in TelecomTV claims that Mobile Social Networking may be the killer application for the promised HSUPA:

This is the year for HSUPA, or High-Speed Uplink Packet Access, according to leading provider of the enabling technology, Qualcomm. HSUPA is the companion standard to HSDPA (the high speed downlink standard) and enables 3G users to upload large files - especially still photos or videos - in seconds rather than minutes.

Qualcomm says that while HSUPA used to be allocated only to the high end chipsets (for use on high end phones) it's now being included as standard for chipsets aimed at 'mid range' devices and by the end of the year will appear as standard on low end phones as well.
Why the adoption spurt? Mobile social networking and user generated contents are the main reason. Where many traditional data applications, such as receiving email, web browsing, and music and video downloading are overwhelmingly asymmetric (far more data coming down than going up) the coming mobile social networking wave looks likely to demand huge amounts of uplink capacity as users begin to use the features of their new upscale phones in earnest. High resolution multi-megapixel cameras mean big, chunky picture files; easy video capture means even larger video files; and new applications involving pictures and location, via GPS, require high quality, reliable connectivity back to the controlling server.

According to Qualcomm, mobile social networking will finally and resoundingly answer the question: Why do we need 3G?

We'll need it because the evidence shows that users are interested in taking social networking out of the confines of the tethered PC, and putting it on the road via their mobiles where it can blend with and enhance real, physical, non-virtual social networking: the sort which involves real people moving about and doing things in real places.

So users are fast moving beyond SMS and towards applications and services which will enable them to really share their activities at, say, live events.

So let HSUPA roll and let the fun begin.

All about F-DPCH

Fractional DPCH was added in Rel-6 to optimise the consumption of downlink channelization codes. When using HS-DSCH (High Speed Downlink Shared Channel), the main use for DL DPCH (also known as A-DPCH where A stands for Associated) is to carry power control commands (TPC bits) to the UE in order to adjust the uplink transmission. If all RBs (Radio Bearers) including SRBs (Signalling Radio Bearers) are mapped on to HS-DSCH then the DL codes are being wasted. SF 256 is used for A-DPCH and so every code being used by a user is seriously depleting the codes available for other UE's. To overcome this F-DPCH is used so that multiple UE's can share a single DL channelisation code. The limitation is 10 UEs in Rel-6.

For several users, the network configures each user having the same code but different frame timing and, thus, users can be transmitted on the single code source. The original timing is thus retained which avoids the need to adjust timings based on Release 99 power control loop implementation.

During slots where the DPCCH is not transmitted, the NodeB cannot estimate the uplink signal-to-interference ratio for power-control purposes and there is no reason for transmitting a power control bit in the downlink. Consequently, the UE shall not receive any power control commands on the F-DPCH in downlink slots corresponding to inactive uplink DPCCH slots.

There are some restrictions for FDPCH. It is not usable with services requiring data to be mapped to the DCH, such as AMR speech calls and CS video. Also, the lack of pilot information means that a method like feedback-based transmit diversity (closed loop mode) is not usable. The use of closed loop diversity is based on user-specific phase modification, wherein pilot symbols would be needed for verification of the phase rotation applied. On the other hand, when utilizing the F-DPCH, SRBs can benefit from high data rates of HSDPA and reduce service setup times remarkably

Finally, as you may have already figured out, by using F-DPCH the cell capacity has been improved and at the same time for same number of users, the interference has gone down significantly.

In Release 7, Rel-6 limitation has been removed. In R6, for a given UE in soft handover the TPC from all F-DPCH had to have the same offset timing. In R7, F-DPCH (TPC bits) can have different timing from different cells. This is possible due to introduction of 9 new F-DPCH slot formats (slot format 0 is the legacy F-DPCH slot format). The RRC signalling is done seperately for slot formats from the RNC to each of the cells.

You may also be interested in this Ericsson paper titled "The effect of F-DPCH on VoIP over HSDPA Capacity". Available here.

3G -> 3.9G

There seems to be confusion when people discuss terms like 3.5G, 3.75G so i decided to define them. I am sure people who have objections will comment.

Lets first start with 2G systems:

2G = GSM

2.5G = GPRS

2.75G = EDGE

Then moving onto 3G systems:

3G = WCDMA, R99 (i am not looking at other technologies but similar mapping will apply)
3.5G = HSDPA

3.75G = HSUPA

3.8G = HSPA+ (HSPA Enhancements)

3.85G = 'HSPA+' + MIMO
3.9G = LTE

4G = NOT WiMAX