HSDPA Code Tree

How often does it happen that people ask you questions you know the answer to but cant recall the complete details. A similar thing happened when a colleague asked me about why only 15 codes why HS-PDSCH and what happens to the 16th code.

Here is a picture which is from Qualcomm Whitepaper (available here) which is self explanatory.

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.

Implementation of CQI Reporting in HSPA

In HSDPA the channel quality indicator is a measure of the mobile channel which is send regularly from the UE to the Node B. These measurements are used to adapt modulation and coding for the corresponding UE and it can be also used for the scheduling algorithms.

The CQI measurement is implemented in the HSPA module and the measurement interval as well as the influence of measurement errors can be parameterised. The results can be given in form of maps or in a statistical manner as histogram for each cell.

Information about the instantaneous channel quality at the UE is typically obtained through a 5-bit Channel-Quality Indicator (CQI) in HS-SCCH, which each UE feed back to the NodeB at regular intervals. The CQI is calculated at the UE based on the signal-to-noise ratio of the received common pilot. Instead of expressing the CQI as a received signal quality, the CQI is expressed as a recommended transport-block size, taking into account also the receiver performance.

The reason for not reporting an explicit channel-quality measure is that different UEs might support different data rates in identical environments, depending on the exact receiver implementation. By reporting the data rate rather than an explicit channel-quality measure, the fact that a UE has a relatively better receiver can be utilized to provide better service (higher data rates) to such a UE. It is interesting to note that this provides a benefit with advanced receiver structures for the end user.

This is appropriate as the quantity of relevance is the instantaneous data rate a terminal can support rather than the channel quality alone. Hence, a terminal with a more advanced receiver, being able to receive data at a higher rate at the same channel quality, will report a larger CQI than a terminal with a less advanced receiver, all other conditions being identical.

Each 5-bit CQI value corresponds to a given transport-block size, modulation scheme, and number of channelization codes. Different tables are used for different UE categories as a UE shall not report a CQI exceeding its capabilities. For example, a UE only supporting 5 codes shall not report a CQI corresponding to 15 codes, while a 15-code UE may do so. Therefore, power

offsets are used for channel qualities exceeding the UE capabilities. A power offset of x dB indicates that the UE can receive a certain transport-block size, but at x dB lower transmission power than the CQI report was based upon. UEs belonging to category 1–6 can only receive up to 5 HS-DSCH channelization codes and therefore must use a power offset for the highest CQI values, while category 10 UEs are able to receive up to 15 codes.

The CQI values listed are sorted in ascending order and the UE shall report the highest CQI for which transmission with parameters corresponding to the CQI result in a block error probability not exceeding 10%.

Specifying which interval the CQI relates to allows the NodeB to track changes in the channel quality between the CQI reports by using the power control commands for the associated downlink (F-) DPCH. The rate of the channel-quality reporting is configurable in the range of one report per 2–160 ms. The CQI reporting can also be switched off completely.

In addition to the instantaneous channel quality, the scheduler implementation in the NodeB should typically also take buffer status and priority levels into account before finalising the data rate for the UE. Obviously UEs for which there is no data awaiting transmission should not be scheduled. There could also be data that is important to transmit within a certain maximum delay, regardless of the channel conditions. One important example hereof is RRC signalling, for example, related to cell change in order to support mobility, which should be delivered to the UE as soon as possible. Another example, although not as time critical as RRC signalling, is streaming services, which has an upper limit on the acceptable delay of a packet to ensure a constant average data rate. To support priority handling in the scheduling decision, a set of priority queues is defined into which the data is inserted according to the priority of the data. The scheduler selects data from these priority queues for transmission based on the channel conditions, the priority of the queue, and any other relevant information.

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

Advanced 3GPP Interference Aware Receivers

Receiver structures in UEs and Node-Bs are constantly being improved as products evolve and more complex features are added to HSPA. The result is improved system performance and higher user data bit rates. This trend is reflected in constantly changing UE receiver requirements in 3GPP. In 2006, 3GPP has studied further improved minimum performance requirements for UMTS/HSDPA UEs. These enhanced performance requirements are release-independent (i.e. apply also to a Rel-6 terminal with advanced receivers).


Interference aware receivers, referred to as type 2i and type 3i, were defined as extensions of the existing type 2 and type 3 receivers, respectively. The basic receiver structure is that of an LMMSE sub-chip level equalizer which takes into account not only the channel response matrix of the serving cell, but also the channel response matrices of the most significant interfering cells. HSDPA throughput estimates were developed using link level simulations, which include the other-cell interference model plus Orthogonal Carrier Noise Simulator (OCNS) models for the serving and interfering cells based on the two network scenarios considered.

This type of receiver attempts to cancel the interference that arises from users operating outside the serving cell, which is also referred to as other-cell interference. Interference models/profiles were developed for this other-cell interference in terms of the number of interfering Node Bs to consider, and their powers relative to the total other cell interference power, the latter ratios referred to as Dominant Interferer Proportion (DIP) ratios. For the purposes of this study item it was determined that five interfering Node Bs should be taken into account in the interference models. DIP ratios were defined based on three criteria: median values of the corresponding cumulative density functions, weighted average throughput gain, and field data. Of these criteria, the one based on the ‘weighted average’ was felt to offer a compromise between the conservative, median value criteria and the more optimistic field data criteria. In addition, two network scenarios were defined, one based solely on HSDPA traffic (HSDPA-only), and the other based on a mixture of HSDPA and Rel-99 voice traffic (HSDPA+R99).

HSDPA throughput estimates were then developed using link level simulations, which included the othercell interference models plus OCNS models for the serving and interfering cells based on the two network scenarios considered. The two-branch reference receiver, referred to as a type 3i receiver, was found to offer significant gains in throughput primarily at or near the cell edge. Link level results were developed for a wide range of operating conditions including such factors as transport format, network scenario, modulation, and channel model. For example, the gains for the DIP ratios based on the weighted average ranged from a factor of 1.2 to 2.05 for QPSK H-SET6 PB3, and from 1.2 to 3.02 for VA30 for network geometries of -3 and 0 dB. This complements the performance of existing two-branch equalizers (type 3), which typically provide gain at high geometries, and thus, the combination of the two will lead to a much better user experience over the entire cell.

In addition, a system level study was conducted that indicated that a type 3i receiver provided gains in coverage ranging from 20-55% for mildly dispersive channels, and 25-35% for heavily dispersive channels, the exact value of which depends upon user location. A second system level study divided the users into two different groups depending on their DCH handover states, where the first group collected users in soft handover (between cells), and the second group collected users in softer handover (between sectors of the same cell). The results of this second study indicate that the Type 3i receiver will provide benefits for users in these two groups, increasing their throughput by slightly over 20%. With regards to implementation issues, it was felt that the type 3i receiver is based upon known and mature signal processing techniques, and thus, the complexity is minimized. With two-branch, equalizer-based receivers already available in today’s marketplace, it appears quite doable to develop a two-branch equalizer with interference cancellation/mitigation capabilities. Given all of the above, 3GPP concluded that two-branch interference cancellation receivers are feasible for HSDPA, and a work item has been created to standardize the performance requirements with type 3i receiver.

More on this topic is available in the following:

• 3GPP TR 25.963 V7.0.0: Feasibility study on interference cancellation for UTRA FDD User Equipment (UE)
• Signal Processing for Wireless Communications By Joseph Boccuzzi
• Simulation results can also be obtained from reports here.

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.

HSPA Data Rates Calculation

People often get lost while calculating the data rates for HSDPA, HSUPA or HSPA+

Note: HSPA+ is better known as eHSPA or HSPAe where e stands for evolution or evolved

Most people are aware that the theoretical maximum for HSDPA is 14.4Mbps, so lets see how we reach 14.4Mbps:

In UMTS, in each slot the maximum number of bits transmitted is 2560. The correct term to use is chips rather than bits. If you want to know where this 2560 comes from or why chips then please refer 3GPP TS 25.211

There are 15 slots per 10ms frame so since the TTI for HSDPA is 2ms, there will be 3 slots. So there will be a total of 7680 chips.

QPSK has 2 bits per symbol = 7680 * 2 chips for 2ms = 15360 chips/2ms = 15360 * 1000 /2 chips per second

Now the SF is fixed at 16
= (15360 * 1000) / (2 * 16)
= 480 Kbps

Terminal that uses 15 QPSK codes will get 480 * 15 = 7.2Mbps

On other hand 16 QAM will have 4 bits per symbol so the rate would be 7.2 * 2 = 14.4Mbps



In HSPA+ we will also have 64QAM which has 6 bits per symbol (2^6 = 64) so the max rate would be 7.2 * 3 = 21.6Mbps.

The figure above is self explanatory and shows the data rate in case of eHSPA.

ZTE now shows off 2Mbps TD-HSDPA

ZTE Corporation a leading global provider of telecommunications equipment and network solutions, showcased its 2M TD-HSDPA high-speed wireless downloading technology solution in line with the company’s theme of “Talking to the Future” at the GSMA Mobile Asia Congress 2007 held from 12th to 14th November 2007 at The Venetian® Macau. The GSMA Mobile Asia Congress (formerly 3GSM World Congress Asia) is the sister event of the Mobile World Congress in Barcelona, and is attended by mobile professionals and innovators from across Asia and around the world.

With its 2M TD-HSDPA technology solution, ZTE clearly shows its vision to further enhance the TD-SCDMA concept and make it a part of consumers’ mobile wireless communication experience. ZTE’s 2M TD-HSDPA technology provides user endpoint’s downstream data rate as high as 2M, allowing users to enjoy smooth high-definition movies online, download documents in bulk, as well as experience many top-line multimedia functions. 2M speed rate is best achieved on 1.6M broadband single carrier, while 20Mbps can be achieved on multi-HSDPA carriers.

HSDPA is a large volume mobile multimedia service 3G technology for GSM-based mobile phones developed by mobile operators to bring true broadband speed wirelessly. It incorporates AMC (Adaptive Modulation and Coding), HARQ (Hybrid Automatic Repeat reQuest), RRM (radio resource management) and MIMO (Multiple-Input Multiple-Out-put) technologies, all of which significantly improve downstream data rate.

“ZTE’s 2M TD-HSDPA showcase at GSMA Mobile Asia Congress Macau builds the momentum of our successful presence in PT/Wireless & Networks Expo Comm in Beijing, China last month,” says Mr. Liang Ming, International Marketing Director of TD-SCDMA products, ZTE Corporation. “As the first provider to showcase TD-MBMS mobile TV solution, we further solidify our remarkable capability in TD area with this solution. As a run-up to the forthcoming Beijing Olympics, ZTE is setting the stage as among the pioneers in providing users in the country with extraordinary TD-SCDMA wireless solutions.”

Turbo 3G ... HSDPA by Stealth

Telenor (Norway) announced the launch of its Turbo 3G network last week. They call it as the first step towards Mobile Broadband. Reading the footnotes gives the game away as they do mention that 'The technical term for Turbo-3G is HSDPA'

This does make it sound better than the normal HSDPA network which would be difficult for laymen to understand. Nut why not simply call it Fast 3G or Super fast 3G (but this term may be better for LTE).

Anyway, their maximum downlink speeds of 3.6Mbps is not very impressive as the theoretical speeds of 14.4Mbps is possible.

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

UMTS/HSDPA MOST WIDELY DEPLOYED 3G TECHNOLOGY

UMTS/HSDPA MOST WIDELY DEPLOYED 3G TECHNOLOGY - 3G Americas Press Release

117 Million 3G Customers use UMTS/HSDPA

Bellevue, WA, May 24, 2007 -
The GSM technology global coverage footprint has provided the foundation for UMTS/HSDPA to become the most widely deployed 3G technology and market leader, with 167 operators in 69 countries offering UMTS services, 115 of whom have enhanced service with HSDPA. 3G Americas reports today that according to Informa‘s World Cellular Information Service quarterly subscriber reports, UMTS/HSDPA, with 117 million subscribers, is commercially available through twice as many operators as other 3G technologies – 167 operators in 69 countries, compared to 71 operators in 44 countries with CDMA EV-DO. Of the 172 million true mobile broadband 3G subscribers worldwide as of 1Q 2007, 68% use UMTS/HSDPA.

The GSM family of technologies currently provides service to 2.4 billion users worldwide, and comprises 85% of the total global wireless mobile market. GSM is the most widely deployed technology in the Western Hemisphere and the only technology present in every country of the region, encompassing 58% of all mobile wireless customers in the Western Hemisphere. Worldwide, the greatest quarterly growth of UMTS/HSDPA took place in the US and Canada, where UMTS experienced an unprecedented 614% growth, rocketing from 350,000 subscribers to 2.5 million subscribers in three months ending March 2007.

Chris Pearson, President of 3G Americas stated, "UMTS/HSDPA technology in North America will continue its steady growth as subscribers become aware of the tremendous applications and devices that make full use of these high speed wireless data networks.” Pearson continued. “The anticipated launch of T-Mobile’s UMTS network in 2007 will continue the 3G momentum in the Americas.”

In the twelve months from March 2006 to March 2007, there were 538 million new GSM/UMTS subscriptions worldwide, compared to 49 million total net additions for CDMA. For the same time period, GSM grew its subscriber base in Latin America and the Caribbean by 80 million new customers for a total of over 231 million GSM users in the region. GSM's regional share of the Latin America market has continued its steady momentum, increasing from 59% in March 2006 to almost 71% in March 2007. The Latin American and Caribbean subscriber base for CDMA concurrently declined by 826,000 customers during the first quarter of 2007.

"2006 was the year we saw HSDPA become widely available across North America, and 2007 will be the year it starts to make its way across Latin America," commented Erasmo Rojas, Director of Latin America and the Caribbean. "Operators in Brazil have announced plans to deploy HSDPA in 850 MHz; Telefonica recently launched HSDPA in Mexico, and the technology has already been launched commercially by AT&T Puerto Rico, Entel Chile and Telecom Personal in Argentina. “

HSPA (HSDPA/HSUPA) is the set of technology enhancements for UMTS standardized by 3GPP that helps define the migration path for GSM operators worldwide to mobile broadband. There are more than 250 HSDPA devices in the market today including smartphones, PDA’s, PC cards USB drives, embedded notebooks and even desktop modems. Announcements have already begun for commercial HSDPA/HSUPA devices that provide peak theoretical throughput rates up to 7.2 Mbps on the downlink. It is expected that virtually all UMTS operators will upgrade to HSDPA, followed by HSUPA, providing them with a significant increase in capacity and data throughput and a reduced network cost for data services.

Subscriber data is based upon information from Informa Telecoms & Media. For charts on GSM growth, visit the 3G Americas website at: http://www.3gamericas.org/.