Showing posts with label 5G Americas. Show all posts
Showing posts with label 5G Americas. Show all posts

Saturday, 4 April 2020

5G eXtended Reality (5G-XR) in 5G System (5GS)


We have been meaning to make a tutorial on augmented reality (AR), virtual reality (VR), mixed reality (MR) and extended reality (XR) for a while but we have only managed to do it. Embedded below is video and slides for the tutorial and also a playlist of different use cases on XR from around the world.

If you are not familiar with the 5G Service Based Architecture (SBA) and 5G Core (5GC), best to check this earlier tutorial before going further. A lot of comments are generally around Wi-Fi instead of 5G being used for indoors and we completely agree. 3GPP 5G architecture is designed to cater for any access in addition to 5G access. We have explained it here and here. This guest post also nicely explains Network Convergence of Mobile, Broadband and Wi-Fi.





XR use cases playlist



A lot of info on this topic is from Qualcomm, GSMA, 3GPP and 5G Americas whitepaper, all of them in the links in the slides.


Related Posts:

Sunday, 19 January 2020

2-step RACH Enhancement for 5G New Radio (NR)

5G Americas recently published a white paper titled, "The 5G Evolution: 3GPP Releases 16-17" highlighting new features in 5G that will define the next phase of 5G network deployments across the globe. It's available here. One of the sections in that details the 2-step RACH enhancement that is being discussed for a while in 3GPP. The 2-step process would supercede the 4-step process today and would reduce the lartency and optimise the signalling.


Here are the details from the 5G Americas whitepaper:

RACH stands for Random Access Channel, which is the first message from UE to eNB when it is powered on. In terms of Radio Access Network implementation, handling RACH design can be one of the most important / critical portions.
The contention-based random-access procedure from Release 15 is a four-step procedure, as shown in Figure 3.12. The UE transmits a contention-based PRACH preamble, also known as Msg1. After detecting the preamble, the gNB responds with a random-access response (RAR), also known as Msg2. The RAR includes the detected preamble ID, a time-advance command, a temporary C-RNTI (TC-RNTI), and an uplink grant for scheduling a PUSCH transmission from the UE known as Msg3. The UE transmits Msg3 in response to the RAR including an ID for contention resolution. Upon receiving Msg3, the network transmits the contention resolution message, also known as Msg4, with the contention resolution ID. The UE receives Msg4, and if it finds its contention-resolution ID it sends an acknowledgement on a PUCCH, which completes the 4-step random access procedure.

The four-step random-access procedure requires two round-trip cycles between the UE and the base station, which not only increases the latency but also incurs additional control-signaling overhead. The motivation of two-step RACH is to reduce latency and control-signaling overhead by having a single round trip cycle between the UE and the base station. This is achieved by combining the preamble (Msg1) and the scheduled PUSCH transmission (Msg3) into a single message (MsgA) from the UE, known as MsgA. Then by combining the random-access respond (Msg2) and the contention resolution message (Msg4) into a single message (MsgB) from the gNB to UE, see Figure 3.13. Furthermore, for unlicensed spectrum, reducing the number of messages transmitted from the UE and the gNB, reduces the number of LBT (Listen Before Talk) attempts.

Design targets for two-step RACH:

  • A common design for the three main uses of 5G, i.e. eMBB, URLLC and mMTC in licensed and unlicensed spectrum.
  • Operation in any cell size supported in Release 15, and with or without a valid uplink time alignment (TA).
  • Applicable to different RRC states, i.e. RRC_INACTIVE, RRC_CONNECTED and RRC_IDLE states.
  • All triggers for four-step RACH apply to two-step RACH including, Msg3-based SI request and contention-based beam failure recovery (CB BFR).

As described earlier, MsgA consists of a PRACH preamble and a PUSCH transmission, known as MsgA PRACH and MsgA PUSCH respectively. The MsgA PRACH preambles are separate from the four-step RACH preambles, but can be transmitted in the same PRACH Occasions (ROs) as the preambles of fourstep RACH, or in separate ROs. The PUSCH transmissions are organized into PUSCH Occasions (POs) which span multiple symbols and PRBs with optional guard periods and guard bands between consecutive POs. Each PO consists of multiple DMRS ports and DMRS sequences, with each DMRS port/DMRS sequence pair known as PUSCH resource unit (PRU). two-step RACH supports at least one-to-one and multiple-to-one mapping between the preambles and PRUs.

After the UE transmits MsgA, it waits for the MsgB response from the gNB. There are three possible outcomes:

  1. gNB doesn’t detect the MsgA PRACH ➡ No response is sent back to the UE ➡ The UE retransmits MsgA or falls back to four-step RACH starting with a Msg1 transmission.
  2. gNB detects MsgA preamble but fails to successful decode MsgA PUSCH ➡ gNB sends back a fallbackRAR to the UE with the RAPID (random-access preamble ID) and an uplink grant for the MsgA PUSCH retransmission ➡ The UE upon receiving the fallbackRAR, falls back to four-step RACH with a transmission of Msg3 (retransmission of the MsgA PUSCH).
  3. gNB detects MsgA and successfully decodes MsgA PUSCH ➡ gNB sends back a successRAR to the UE with the contention resolution ID of MsgA ➡ The reception of the successRAR successfully completes the two-step RACH procedure.

As described earlier, MsgB consists of the random-access response and the contention-resolution message. The random-access response is sent when the gNB detects a preamble but cannot successfully decode the corresponding PUSCH transmission. The contention resolution message is sent after the gNB successfully decodes the PUSCH transmission. MsgB can contain backoff indication, fallbackRAR and/or successRAR. A single MsgB can contain the successRAR of one or more UEs. The fallbackRAR consists of the RAPID: an uplink grant to retransmit the MsgA PUSCH payload and time-advance command. The successRAR consists of at least the contention resolution ID, the C-RNTI and the TA command.

For more details on this feature, see 3GPP RP-190711, “2-step RACH for NR” (Work-item description)

Monday, 1 May 2017

Variety of 3GPP IoT technologies and Market Status - May 2017



I have seen many people wondering if so many different types of IoT technologies are needed, 3GPP or otherwise. The story behind that is that for many years 3GPP did not focus too much on creating an IoT variant of the standards. Their hope was that users will make use of LTE Cat 1 for IoT and then later on they created LTE Cat 0 (see here and here).

The problem with this approach was that the market was ripe for a solution to a different types of IoT technologies that 3GPP could not satisfy. The table below is just an indication of the different types of technologies, but there are many others not listed in here.


The most popular IoT (or M2M) technology to date is the humble 2G GSM/GPRS. Couple of weeks back Vodafone announced that it has reached a milestone of 50 million IoT connections worldwide. They are also adding roughly 1 million new connections every month. The majority of these are GSM/GPRS.

Different operators have been assessing their strategy for IoT devices. Some operators have either switched off or are planning to switch off they 2G networks. Others have a long term plan for 2G networks and would rather switch off their 3G networks to refarm the spectrum to more efficient 4G. A small chunk of 2G on the other hand would be a good option for voice & existing IoT devices with small amount of data transfer.

In fact this is one of the reasons that in Release-13 GSM is being enhanced for IoT. This new version is known as Extended Coverage – GSM – Internet of Things (EC-GSM-IoT ). According to GSMA, "It is based on eGPRS and designed as a high capacity, long range, low energy and low complexity cellular system for IoT communications. The optimisations made in EC-GSM-IoT that need to be made to existing GSM networks can be made as a software upgrade, ensuring coverage and accelerated time to-market. Battery life of up to 10 years can be supported for a wide range use cases."

The most popular of the non-3GPP IoT technologies are Sigfox and LoRa. Both these technologies have gained significant ground and many backers in the market. This, along with the gap in the market and the need for low power IoT technologies that transfer just a little amount of data and has a long battery life motivated 3GPP to create new IoT technologies that were standardised as part of Rel-13 and are being further enhanced in Rel-14. A summary of these technologies can be seen below


If you look at the first picture on the top (modified from Qualcomm's original here), you will see that these different IoT technologies, 3GPP or otherwise address different needs. No wonder many operators are using the unlicensed LPWA IoT technologies as a starting point, hoping to complement them by 3GPP technologies when ready.

Finally, looks like there is a difference in understanding of standards between Ericsson and Huawei and as a result their implementation is incompatible. Hopefully this will be sorted out soon.


Market Status:

Telefonica has publicly said that Sigfox is the best way forward for the time being. No news about any 3GPP IoT technologies.

Orange has rolled out LoRa network but has said that when NB-IoT is ready, they will switch the customers on to that.

KPN deployed LoRa throughout the Netherlands thereby making it the first country across the world with complete coverage. Haven't ruled out NB-IoT when available.

SK Telecom completed nationwide LoRa IoT network deployment in South Korea last year. It sees LTE-M and LoRa as Its 'Two Main IoT Pillars'.

Deutsche Telekom has rolled out NarrowBand-IoT (NB-IoT) Network across eight countries in Europe (Germany, the Netherlands, Greece, Poland, Hungary, Austria, Slovakia, Croatia)

Vodafone is fully committed to NB-IoT. Their network is already operational in Spain and will be launching in Ireland and Netherlands later on this year.

Telecom Italia is in process of launching NB-IoT. Water meters in Turin are already sending their readings using NB-IoT.

China Telecom, in conjunction with Shenzhen Water and Huawei launched 'World's First' Commercial NB-IoT-based Smart Water Project on World Water Day.

SoftBank is deploying LTE-M (Cat-M1) and NB-IoT networks nationwide, powered by Ericsson.

Orange Belgium plans to roll-out nationwide NB-IoT & LTE-M IoT Networks in 2017

China Mobile is committed to 3GPP based IoT technologies. It has conducted outdoor trials of NB-IoT with Huawei and ZTE and is also trialing LTE-M with Ericsson and Qualcomm.

Verizon has launched Industry’s first LTE-M Nationwide IoT Network.

AT&T will be launching LTE-M network later on this year in US as well as Mexico.

Sprint said it plans to deploy LTE Cat 1 technology in support of the Internet of Things (IoT) across its network by the end of July.

Further reading:

Sunday, 6 November 2016

LTE, 5G and V2X

3GPP has recently completed the Initial Cellular V2X standard. The following from the news item:

The initial Cellular Vehicle-to-Everything (V2X) standard, for inclusion in the Release 14, was completed last week - during the 3GPP RAN meeting in New Orleans. It focuses on Vehicle-to-Vehicle (V2V) communications, with further enhancements to support additional V2X operational scenarios to follow, in Release 14, targeting completion during March 2017.
The 3GPP Work Item Description can be found in RP-161894.
V2V communications are based on D2D communications defined as part of ProSe services in Release 12 and Release 13 of the specification. As part of ProSe services, a new D2D interface (designated as PC5, also known as sidelink at the physical layer) was introduced and now as part of the V2V WI it has been enhanced for vehicular use cases, specifically addressing high speed (up to 250Kph) and high density (thousands of nodes).

...


For distributed scheduling (a.k.a. Mode 4) a sensing with semi-persistent transmission based mechanism was introduced. V2V traffic from a device is mostly periodic in nature. This was utilized to sense congestion on a resource and estimate future congestion on that resource. Based on estimation resources were booked. This technique optimizes the use of the channel by enhancing resource separation between transmitters that are using overlapping resources.
The design is scalable for different bandwidths including 10 MHz bandwidth.
Based on these fundamental link and system level changes there are two high level deployment configurations currently defined, and illustrated in Figure 3.
Both configurations use a dedicated carrier for V2V communications, meaning the target band is only used for PC5 based V2V communications. Also in both cases GNSS is used for time synchronization.
In “Configuration 1” scheduling and interference management of V2V traffic is supported based on distributed algorithms (Mode 4) implemented between the vehicles. As mentioned earlier the distributed algorithm is based on sensing with semi-persistent transmission. Additionally, a new mechanism where resource allocation is dependent on geographical information is introduced. Such a mechanism counters near far effect arising due to in-band emissions.
In “Configuration 2” scheduling and interference management of V2V traffic is assisted by eNBs (a.k.a. Mode 3) via control signaling over the Uu interface. The eNodeB will assign the resources being used for V2V signaling in a dynamic manner.

5G Americas has also published a whitepaper on V2X Cellular Solutions. From the press release:

Vehicle-to-Everything (V2X) communications and solutions enable the exchange of information between vehicles and much more - people (V2P), such as bicyclists and pedestrians for alerts, vehicles (V2V) for collision avoidance, infrastructure (V2I) such as roadside devices for timing and prioritization, and the network (V2N) for real time traffic routing and other cloud travel services. The goal of V2X is to improve road safety, increase the efficiency of traffic, reduce environmental impacts and provide additional traveler information services. 5G Americas, the industry trade association and voice of 5G and LTE for the Americas, today announced the publication of a technical whitepaper titled V2X Cellular Solutions that details new connected car opportunities for the cellular and automotive industries.




The whitepaper describes the benefits that Cellular V2X (C-V2X) can provide to support the U.S. Department of Transportation objectives of improving safety and reducing vehicular crashes. Cellular V2X can also be instrumental in transforming the transportation experience by enhancing traveler and traffic information for societal goals.

C-V2X is part of the 3GPP specifications in Release 14. 3GPP announced the completion of the initial C-V2X standard in September 2016. There is a robust evolutionary roadmap for C-V2X towards 5G with a strong ecosystem in place. C-V2X will be a key technology enabler for the safer, more autonomous vehicle of the future.

The whitepaper is embedded below:




Related posts:
Further Reading:



Sunday, 16 October 2016

Inside 3GPP Release-13 - Whitepaper by 5G Americas


The following is from the 5G Americas press release:

The summary offers insight to the future of wireless broadband and how new requirements and technological goals will be achieved. The report updates Release 13 (Rel-13) features that are now completed at 3GPP and were not available at the time of the publication of a detailed 5G Americas report, Mobile Broadband Evolution Towards 5G: 3GPP Release 12 & Release 13 and Beyond in June 2015.
The 3GPP standards have many innovations remaining for LTE to create a foundation for 5G.  Rel-12, which was finalized in December 2014, contains a vast array of features for both LTE and HSPA+ that bring greater efficiency for networks and devices, as well as enable new applications and services. Many of the Rel-12 features were extended into Rel-13.  Rel-13, functionally frozen in December 2015 and completed in March 2016, continues to build on these technical capabilities while adding many robust new features.
Jim Seymour, Principal Engineer, Mobility CTO Group, Cisco and co-leader of the 5G Americas report explained, “3GPP Release 13 is just a peek behind the curtain for the unveiling of future innovations for LTE that will parallel the technical work at 3GPP on 5G. Both LTE and 5G will work together to form our connected future.”
The numerous features in the Rel-13 standards include the following for LTE-Advanced:
  • Active Antenna Systems (AAS), including beamforming, Multi-Input Multi-Output (MIMO) and Self-Organizing Network (SON) aspects
  • Enhanced signaling to support inter-site Coordinated Multi-Point Transmission and Reception (CoMP)
  • Carrier Aggregation (CA) enhancements to support up to 32 component carriers
  • Dual Connectivity (DC) enhancements to better support multi-vendor deployments with improved traffic steering
  • Improvements in Radio Access Network (RAN) sharing
  • Enhancements to Machine Type Communication (MTC)
  • Enhanced Proximity Services (ProSe)
Some of the standards work in Rel-13 related to spectrum efficiency include:                                                                                                                       
  • Licensed Assisted Access for LTE (LAA) in which LTE can be deployed in unlicensed spectrum
  • LTE Wireless Local Area Network (WLAN) Aggregation (LWA) where Wi-Fi can now be supported by a radio bearer and aggregated with an LTE radio bearer
  • Narrowband IoT (NB-IoT) where lower power wider coverage LTE carriers have been designed to support IoT applications
  • Downlink (DL) Multi-User Superposition Transmission (MUST) which is a new concept for transmitting more than one data layer to multiple users without time, frequency or spatial separation
“The vision for 5G is being clarified in each step of the 3GPP standards. To understand those steps, 5G Americas provides reports on the developments in this succinct, understandable format,” said Vicki Livingston, Head of Communications for the association.

The whitepaper as follows:



Related posts:

Saturday, 12 December 2015

LTE-Advanced Pro (a.k.a. 4.5G)

3GPP announced back in October that the next evolution of the 3GPP LTE standards will be known as LTE-Advanced Pro. I am sure this will be shortened to LTE-AP in presentations and discussions but should not be confused with access points.

The 3GPP press release mentioned the following:

LTE-Advanced Pro will allow mobile standards users to associate various new features – from the Release’s freeze in March 2016 – with a distinctive marker that evolves the LTE and LTE-Advanced technology series.

The new term is intended to mark the point in time where the LTE platform has been dramatically enhanced to address new markets as well as adding functionality to improve efficiency.

The major advances achieved with the completion of Release 13 include: MTC enhancements, public safety features – such as D2D and ProSe - small cell dual-connectivity and architecture, carrier aggregation enhancements, interworking with Wi-Fi, licensed assisted access (at 5 GHz), 3D/FD-MIMO, indoor positioning, single cell-point to multi-point and work on latency reduction. Many of these features were started in previous Releases, but will become mature in Release 13.

LTE-evolution timelinea 350pxAs well as sign-posting the achievements to date, the introduction of this new marker confirms the need for LTE enhancements to continue along their distinctive development track, in parallel to the future proposals for the 5G era.


Some vendors have been exploring ways of differentiating the advanced features of Release-13 and have been using the term 4.5G. While 3GPP does not officially support 4.5G (or even 4G) terminology, a new term has been welcomed by operators and vendors alike.

I blogged about Release-13 before, here, which includes a 3GPP presentation and 4G Americas whitepaper. Recently Nokia (Networks) released a short and sweet video and a whitepaper. Both are embedded below:



The Nokia whitepaper (table of contents below) can be downloaded from here.


Monday, 14 September 2015

3GPP Release-13 whitepapers and presentations

With 3GPP Release-13 due early/mid next year, there has been a flurry of presentations and whitepapers on this topic. This post provides some of these. I will try and maintain a list of whitepapers/presentations as part of this post as and when released.

1. June 2015: LTE Release 13 and road to 5G - Presented by Dino Flore, Chairman of 3GPP RAN, (Qualcomm Technologies Inc.)



2. Sep 2015: Executive Summary - Inside 3GPP Release 13 by 4G Americas



3. June 2015: Mobile Broadband Evolution Towards 5G: 3GPP Rel-12 & Rel-13 and Beyond by 4G Americas

4. April 2015: LTE release 13 – expanding the Networked Society by Ericsson


Sunday, 25 August 2013

Centralized SON


I was going through the presentation by SKT that I blogged about here and came across this slide above. SKT is clearly promoting the benefits of their C-SON (centralized SON) here.


The old 4G Americas whitepaper (here) explained the differences between the three approaches; Centralized (C-SON), Distributed (D-SON) and Hybrid (H-SON). An extract from that paper here:

In a centralized architecture, SON algorithms for one or more use cases reside on the Element Management System (EMS) or a separate SON server that manages the eNB's. The output of the SON algorithms namely, the values of specific parameters, are then passed to the eNB's either on a periodic basis or when needed. A centralized approach allows for more manageable implementation of the SON algorithms. It allows for use case interactions between SON algorithms to be considered before modifying SON parameters. However, active updates to the use case parameters are delayed since KPIs and UE measurement information must be forwarded to a centralized location for processing. Filtered and condensed information are passed from the eNB to the centralized SON server to preserve the scalability of the solution in terms of the volume of information transported. Less information is available at the SON server compared to that which would be available at the eNB. Higher latency due to the time taken to collect UE information restricts the applicability of a purely centralized SON architecture to those algorithms that require slower response time. Furthermore, since the centralized SON server presents a single point of failure, an outage in the centralized server or backhaul could result in stale and outdated parameters being used at the eNB due to likely less frequent updates of SON parameters at the eNB compared to that is possible in a distributed solution.

In a distributed approach, SON algorithms reside within the eNB’s, thus allowing autonomous decision making at the eNB's based on UE measurements received on the eNB's and additional information from other eNB's being received via the X2 interface. A distributed architecture allows for ease of deployment in multi-vendor networks and optimization on faster time scales. Optimization could be done for different times of the day. However, due to the inability to ensure standard and identical implementation of algorithms in a multi-vendor network, careful monitoring of KPIs is needed to minimize potential network instabilities and ensure overall optimal operation.

In practical deployments, these architecture alternatives are not mutually exclusive and could coexist for different purposes, as is realized in a hybrid SON approach. In a hybrid approach, part of a given SON optimization algorithm are executed in the NMS while another part of the same SON algorithm could be executed in the eNB. For example, the values of the initial parameters could be done in a centralized server and updates and refinement to those parameters in response to the actual UE measurements could be done on the eNB's. Each implementation has its own advantages and disadvantages. The choice of centralized, distributed or hybrid architecture needs to be decided on a use-case by use case basis depending on the information availability, processing and speed of response requirements of that use case. In the case of a hybrid or centralized solution, a practical deployment would require specific partnership between the infrastructure vendor, the operator and possibly a third party tool company. Operators can choose the most suitable approach depending upon the current infrastructure deployment.

Finally, Celcite CMO recently recently gave an interview on this topic on Thinksmallcell here. An extract below:

SON software tunes and optimises mobile network performance by setting configuration parameters in cellsites (both large and small), such as the maximum RF power levels, neighbour lists and frequency allocation. In some cases, even the antenna tilt angles are updated to adjust the coverage of individual cells.

Centralised SON (C-SON) software co-ordinates all the small and macrocells, across multiple radio technologies and multiple vendors in a geographic region - autonomously updating parameters via closed loop algorithms. Changes can be as frequent as every 15 minutes– this is partly limited by the bottlenecks of how rapidly measurement data is reported by RAN equipment and also the capacity to handle large numbers of parameter changes. Different RAN vendor equipment is driven from the same SON software. A variety of data feeds from the live network are continuously monitored and used to update system performance, allowing it to adapt automatically to changes throughout the day including outages, population movement and changes in services being used.

Distributed SON (D-SON) software is autonomous within each small cell (or macrocell) determining for itself the RF power level, neighbour lists etc. based on signals it can detect itself (RF sniffing) or by communicating directly with other small cells.

LTE has many SON features already designed in from the outset, with the X.2 interface specifically used to co-ordinate between small and macrocell layers whereas 3G lacks SON standards and requires proprietary solutions.
C-SON software is available from a relatively small number of mostly independent software vendors, while D-SON is built-in to each small cell or macro node provided by the vendor. Both C-SON and D-SON will be needed if network operators are to roll out substantial numbers of small cells quickly and efficiently, especially when more tightly integrated into the network with residential femtocells.

Celcite is one of the handful of C-SON software solution vendors. Founded some 10 years ago, it has grown organically by 35% annually to 450 employees. With major customers in both North and South America, the company is expanding from 3G UMTS SON technology and is actively running trials with LTE C-SON.

Quite a few companies are claiming to be in the SON space, but Celcite would argue that there are perhaps only half a dozen with the capabilities for credible C-SON solutions today. Few companies can point to live deployments. As with most software systems, 90% of the issues arise when something goes wrong and it's those "corner cases" which take time to learn about and deal with from real-world deployment experience.

A major concern is termed "Runaway SON" where the system goes out of control and causes tremendous negative impact on the network. It's important to understand when to trigger SON command and when not to. This ability to orchestrate and issue configuration commands is critical for a safe, secure and effective solution.

Let me know your opinions via comments below.

Monday, 27 February 2012

Voice over HSPA (VoHSPA) and CS over HSPA (CSoHS)


4G Americas has recently released a whitepaper entitled, "Delivering voice over HSPA". This paper describes the technological features that are being developed to make Voice over HSPA (VoHSPA) a reality. It describes the two potential options for VoHSPA. The first option leverages IP Multimedia Subsystem (IMS) technology developed in conjunction with Long Term Evolution (LTE), and is referred to as IMS Voice over HSPA or simply IMS Voice. The other option delivers voice by modifying existing circuit-switch based techniques so that those communications can be transmitted over an HSPA infrastructure, and is referred to as CS Voice over HSPA (CSoHS). Both the options are shown in the picture above. Note that there is no discussion about Over the top (OTT) type voice services like Skype, etc. 

The chief among benefits anticipated from VoHSPA are increases in the spectral efficiency of mobile networks. With these new techniques, voice calls can be delivered more efficiently from a spectral standpoint over Packet Switched (PS) rather than Circuit Switched (CS) networks freeing up radio resources for additional data traffic.


The 4G Americas report defines work completed by the GSMA for a minimum mandatory set of features defined in existing 3GPP Release 8 specifications (IR 58: IMS Profile for VoHSPA) that should be implemented in order to insure an interoperable, high quality, IMS-based telephony service over an HSPA radio access layer. In the white paper, 4G Americas recommends additional features, above the minimum mandatory features in IR 58, for VoHSPA either under an IMS or a CS approach, in order to minimize packet losses and variations in packet arrival times that can impair the quality of voice communications.

The whitepaper is available to download from here.

Monday, 21 November 2011

HSDPA multiflow data transmission

From RP-111375:

HSPA based mobile internet offerings are becoming very popular and data usage is increasing rapidly. As a result, HSPA has begun to be deployed on more than one transmit antenna and/or on more than one carrier. As an example, the single cell downlink MIMO (MIMO-Physical layer) feature was introduced in Release 7. This feature allowed a NodeB to transmit two transport blocks to a single UE from the same cell on a pair of transmit antennas thus improving data rates at high geometries and providing a beamforming advantage to the UE in low geometry conditions. Subsequently, in Release-8 and Release-9, the dual cell HSDPA (DC-HSDPA) and dual band DC-HSDPA features were introduced. Both these features allow the NodeB to serve one or more users by simultaneous operation of HSDPA on two different carrier frequencies in two geographically overlapping cells, thus improving the user experience across the entire cell coverage area.

When a UE falls into the softer or soft handover coverage region of two cells on the same carrier frequency, the link from the serving HS-DSCH cell is capacity or coverage limited and the non-serving cell in its active set has available resources, it would be beneficial to schedule packets to this UE also from the non-serving cell and thereby improve this particular user’s experience.


One family of such schemes parses the incoming data for the user into multiple (restricted to two cells in the study) data streams or flows, each of which is transmitted from a different cell [8] Concurrent transmission of data from the two cells may either be permitted or the UE may be restricted to receiving data from only one cell during a given TTI. The former type of scheme is designated an aggregation scheme while the latter is termed a switching scheme. The aggregation scheme can be seen as subsuming the switching scheme at the network when scheduling to the user is restricted to the cell with better channel quality.

Figure 14 illustrates the basic multi-flow concept with both cells operating on the same carrier frequency F1.




3GPP studied different multipoint transmission options for HSDPA and documented the findings and performance gains in TR25.872 providing feasibility and performance justification for the specification work.

For more details also see:
http://www.3gpp.org/ftp/Specs/html-info/FeatureOrStudyItemFile-530034.htm
See also old blog post on Multipoint HSDPA/HSPA here.

Wednesday, 26 October 2011

New 4G Americas whitepaper on HSPA evolution in 3GPP standards

Some forecasts put HSPA at over 3.5 billion subscribers by the end of 2016. Operators with HSPA and LTE infrastructure and users with HSPA and LTE multi-mode devices will be commonplace. There are 412 commercial deployments of HSPA in 157 countries, including 165 HSPA+ networks. Thus, with the continued deployment of LTE throughout the world, and the existing ubiquitous coverage of HSPA in the world, HSPA+ will continue to be enhanced through the 3GPP standards process to provide a seamless solution for operators as they upgrade their networks. While LTE, with 33 commercial deployments to date and over 250 commitments worldwide, will be the mobile broadband next generation technology of choice for HSPA, EV-DO, WiMAX and new wireless operators, HSPA will continue to be a pivotal technology in providing mobile broadband to subscribers.

The white paper explains that as 3GPP specifications evolve, their advanced features help to further the capabilities of today’s modern mobile broadband networks. With each release there have been improvements such as better cell edge performance, increased system efficiencies, higher peak data rates and an overall improved end-user experience. 3GPP feature evolution from Rel-7 to Rel-10 has pushed possible HSPA peak data rates from 14 Mbps to 168 Mbps. Continued enhancements in 3GPP Rel-11 will again double this capability to a possible peak data rate of 336 Mbps:
  • Rel-7: 64QAM or 2X2 MIMO => 21 or 28 Mbps
  • Rel-8: DC + 64QAM or 2X2 MIMO + 64QAM => 42 Mbps
  • Rel-9: DC + 2X2 MIMO + 64QAM => 84 Mbps
  • Rel-10: 4C + 2X2 MIMO + 64QAM => 168 Mbps
  • Rel-11: (8C or 4X4 MIMO) + 64QAM => 336 Mbps
“If operators are able to gain new additional harmonized spectrum from governments, they will no doubt deploy LTE, However, it is clear that HSPA+ technology is still exceptionally strong and will continue to provide operators with the capability to meet the exploding data usage demands of their customers in existing spectrum holdings,” Pearson said.

The paper is embedded as follows:

This paper and other similar papers are available to download from the 3G4G website here.

Monday, 12 September 2011

LTE Rollouts and Deployment Scenarios

According to GSA report, as of August 2011, 26 commercial LTE networks in 18 countries are already rolled out as below:
As of Aug. 2011, 237 operators in 85 countries are investing in LTE:

* 174 LTE network commitments in 64 countries
* 63 pre-commitment trials in 21 more countries
* 26 commercial LTE networks launched
* At least 93 LTE networks are expected to be in commercial service by end 2012

The following is from the 4G Americas whitepaper:

There are many different scenarios that operators will use to migrate from their current networks to future technologies such as LTE. Figure 10 presents various scenarios including operators who today are using CDMA2000, UMTS, GSM and WiMAX. For example, as shown in the first bar, a CMDA2000 operator in scenario A could defer LTE deployment to the longer term. In scenario B, in the medium term, the operator could deploy a combination of 1xRTT, EV-DO Rev A/B and LTE and, in the long term, could migrate EV-DO data traffic to LTE. In scenario C, a CDMA2000 operator with just 1xRTT could introduce LTE as a broadband service and, in the long term, could migrate 1xRTT users to LTE including voice service.


3GPP and 3GPP2 both have specified detailed migration options for current 3G systems (UMTS-HSPA and EV-DO) to LTE. Due to economies of scale for infrastructure and devices, 3GPP operators are likely to have a competitive cost advantage over Third Generation Partnership Project 2 (3GPP2) operators. One option for GSM operators that have not yet committed to UMTS, and do not have an immediate pressing need to do so, is to migrate directly from GSM/EDGE or Evolved EDGE to LTE with networks and devices supporting dual-mode GSM-EDGE/LTE operation.

Saturday, 10 September 2011

Monday, 14 February 2011

Non-Voice Emergency Services (NOVES)

Its been a while we talked about SMS for Emergency purposes and eCall. A new study item in 3GPP has looked at non-voice alternatives for Emergency purposes.

Picture Source: Dailymail

The following is from the recent 4G Americas report entitled: 4G Mobile Broadband Evolution: 3GPP Release-10 and Beyond:

Non-verbal communications such as text messaging and instant messaging via wireless devices has been very successful and continues to expand. Many of the consumers assume that they can utilize these types of non-verbal communications as mechanisms to communicate with emergency services whenever emergency assistance is required. Such mechanisms currently do not exist. The Emergency Services community has a desire to have multimedia emergency services supported with the same general characteristics as emergency voice calls.

Currently, service requirements for emergency calls (with or without the IP Multimedia Core Network) are limited to voice media. The Non-Voice Emergency Services (NOVES) is intended to be an end-to-end citizen to authority communications. NOVES could support the following examples of non-verbal communications to an emergency services network:
1. Text messages from citizen to emergency services
2. Session-based and session-less instant messaging type sessions with emergency services
3. Multimedia (e.g., pictures, video clips) transfer to emergency services either during or after other communications with emergency services.
4. Real-time video session with emergency services

In addition, to support the general public, this capability would facilitate emergency communications to emergency services by individuals with special needs (e.g., hearing impaired citizens).

The objectives of this study include the following questions for NOVES with media other than or in addition to voice:
1. What are the requirements for NOVES?
2. What are the security, reliability, and priority handling requirements for NOVES?
3. How is the appropriate recipient emergency services system (e.g., PSAP) determined?
4. What are the implications due to roaming?
5. Are there any implications to hand over between access networks?
6. Are there any implications due to the subscriber crossing a PSAP boundary during NOVES communications (e.g., subsequent text messages should go to the same PSAP)?
7. Do multiple communication streams (e.g., voice, text, video emergency services) need to be associated together?
8. What types of “call-back” capabilities are required?
9. What are the load impacts of NOVES in the case of a large scale emergency event or malicious use?

NOVES will be applicable to GPRS (GERAN, UTRAN) and to EPS (GERAN, UTRAN, E-UTRAN and non-3GPP). The content may be transmitted between the subscribers and the emergency services which might bring new security issues. Therefore, the security impacts need to be studied.

You can spend your weekend reading the 3GPP Study Item TR 22.871: Study on Non-Voice Emergency Services (Release 11).

A word of caution, the name NOVES may be changed in future as Emergency agencies in Europe have an objection to the name. See here and here.

Tuesday, 8 February 2011

VoLTE: Semi-Persistent Scheduling (SPS) and TTI Bundling

The following is from the recently released 4G Americas paper '4G Mobile Broadband Evolution: 3GPP Release-10 and beyond:

With the support of emergency and location services in Rel-9, interest in Voice over LTE (VoLTE) has increased. This is because the Rel-9 enhancements to support e911 were the last step to enable VoLTE (at least in countries that mandate e911) since the Rel-8 specifications already included the key LTE features required to support good coverage, high capacity/quality VoLTE. There are two main features in Rel-8 that focus on the coverage, capacity and quality of VoLTE: Semi-Persistent Scheduling (SPS) and TTI Bundling.

SPS is a feature that significantly reduces control channel overhead for applications that require persistent radio resource allocations such as VoIP. In LTE, both the DL and UL are fully scheduled since the DL and UL traffic channels are dynamically shared channels. This means that the physical DL control channel (PDCCH) must provide access grant information to indicate which users should decode the physical DL shared channel (PDSCH) in each subframe and which users are allowed to transmit on the physical UL shared channel (PUSCH) in each subframe. Without SPS, every DL or UL physical resource block (PRB) allocation must be granted via an access grant message on the PDCCH. This is sufficient for most bursty best effort types of applications which generally have large packet sizes and thus typically only a few users must be scheduled each subframe. However, for applications that require persistent allocations of small packets (i.e. VoIP), the access grant control channel overhead can be greatly reduced with SPS.

SPS therefore introduces a persistent PRB allocation that a user should expect on the DL or can transmit on the UL. There are many different ways in which SPS can setup persistent allocations, and Figure below shows one way appropriate for VoLTE. Note that speech codecs typically generate a speech packet every 20 ms. In LTE, the HARQ interlace time is 8 ms which means retransmissions of PRBs that have failed to be decoded can occur every 8 ms. Figure below shows an example where a maximum of five total transmissions (initial transmission plus four retransmissions) is assumed for each 20 ms speech packet with two parallel HARQ processes. This figure clearly shows that every 20 ms a new “first transmission” of a new speech packet is sent. This example does require an additional 20 ms of buffering in the receiver to allow for four retransmissions, but this is generally viewed as a good tradeoff to maximize capacity/coverage (compared to only sending a maximum of two retransmissions).

The example in Figure above can be applied to both the DL and UL and note that as long as there are speech packets arriving (i.e. a talk spurt) at the transmitter, the SPS PRBs would be dedicated to the user. Once speech packets stop arriving (i.e. silence period), these PRB resources can be re-assigned to other users. When the user begins talking again, a new SPS set of PRBs would be assigned for the duration of the new talkspurt. Note that dynamic scheduling of best effort data can occur on top of SPS, but the SPS allocations would take precedent over any scheduling conflicts.


TTI bundling is another feature in Rel-8 that optimizes the UL coverage for VoLTE. LTE defined 1 ms subframes as the Transmission Time Interval (TTI) which means scheduling occurs every 1 ms. Small TTIs are good for reducing round trip latency, but do introduce challenges for UL VoIP coverage. This is because on the UL, the maximum coverage is realized when a user sends a single PRB spanning 180 kHz of tones. By using a single 180 kHz wide PRB on the UL, the user transmit power/Hz is maximized. This is critical on the UL since the user transmit power is limited, so maximizing the power/Hz improves coverage. The issue is that since the HARQ interlace time is 8 ms, the subframe utilization is very low (1/8). In other words, 7/8 of the time the user is not transmitting. Therefore, users in poor coverage areas could be transmitting more power when a concept termed TTI bundling (explained in the next paragraph) is deployed.

While it’s true that one fix to the problem is to just initiate several parallel HARQ processes to fill in more of the 7/8 idle time, this approach adds significant IP overhead since each HARQ process requires its own IP header. Therefore, TTI bundling was introduced in Rel-8 which combined four subframes spanning 4 ms. This allowed for a single IP header over a bundled 4 ms TTI that greatly improved the subframe utilization (from 1/8 to 1/2) and thus the coverage (by more than 3 dB).

Martin Sauter puts it in a simpler way in his blog as follows: The purpose of TTI Bundling is to improve cell edge coverage and in-house reception for voice. When the base station detects that the mobile can't increase it's transmission power and reception is getting worse it can instruct the device to activate TTI bundling and send the same packet but with different error detection and correction bits in 2, 3 or even 4 consecutive transmit time intervals. The advantage over sending the packet in a single TTI and then detecting that it wasn't received correctly which in turn would lead to one or more retransmissions is that it saves a lot of signaling overhead. Latency is also reduced as no waiting time is required between the retransmissions. In case the bundle is not received correctly, it is repeated in the same way as an ordinary transmission of a packet. Holma and Toskala anticipate a 4dB cell edge gain for VoIP with this feature which is quite a lot. For details how the feature is implemented have a look at 3GPP TS 36.321.

A whitepaper explaining the concepts of TTI Bundling is available on Slideshare here.

Tuesday, 19 October 2010

LTE Self Optimizing Networks (SON) enhancements for Release-10

Capacity and Coverage Optimisation (CCO) was already nominally part of the Release-9 WI, but could not be completed due to amount of work related to other use cases.

Energy Savings are a very important topic, especially for operators, as solutions derived for this use case can significantly limit their expenses. According to TR 36.902 this solution should concern switching off cells or whole base stations. This may require additional standardised methods, once there is need identified for.

Basic functionality of Mobility Load Balancing (MLB) and Mobility Robustness Optimisation (MRO), also listed in TR 36.902, were defined in Rel.9. However, successful roll-out of the LTE network requires analysing possible enhancements to the Rel.9 solutions for MLB and MRO. In particular, enhancements that address inter-RAT scenarios and inter-RAT information exchange must be considered. These enhancements should be addressed in Rel.10.

There may also be other use cases for LTE for which SON functionality would bring optimisations.

Although, it is of primary interest to provide coverage to users during a roll-out, it is equally important to enhance the capacity of the network during operation. As such, both coverage and capacity are considered in the use case and supported by the SON function. The CCO SON function should be configured through appropriate objectives and targets in order to meet the operator’s requirement on coverage and capacity, and the prioritization between them.

The following use cases and scenarios are planned for Release-10:

Coverage and Capacity Optimisation (CCO)
The use case is to enable detection of following problems:
Priority 1: coverage problems, e.g. coverage holes
Priority 2: capacity problems

Mobility Robustness Optimisation (MRO) enhancements
The use case is to enable detection and to provide tools for possible correction of following problems:
Connection failures in inter-RAT environment:
o Priority 1: at HOs from LTE to UMTS/GSM
o Priority 2: at HOs from UMTS/GSM to LTE
Obtaining UE measurements in case of unsuccessful re-establishment after connection
failure
Ping-pongs in idle mode (inter-RAT and intra-LTE environment)
Ping-pongs in active mode (inter-RAT)
HO to wrong cell (in intra-LTE environment) that does not cause connection failure (e.g. short stay problem)

Mobility Load Balancing (MLB) enhancements
The use case is to fulfil following objectives:
Improving reliability of MLB in intra-LTE scenarios
Improving functionality of the MLB in inter-RAT scenarios (the transport method agreed for R9 should be used for R10).

For more info see 3GPP TS 32.521: Self-Organizing Networks (SON) Policy Network Resource Model (NRM) Integration Reference Point (IRP); Requirements; Release-10

There is also a Self-Organising Networks Conference that I am attending next month and I plan to give SON lots of coverage before and after the event.

If you havent read the 3G Americas whitepaper on SON, it is definitely worth a read. I have embedded it below.