Parallel Wireless is Hiring

Showing posts with label WiFi. Show all posts
Showing posts with label WiFi. Show all posts

Thursday, 20 July 2017

Second thoughts about LTE-U / LAA

Its been a while since I wrote about LTE-U / LAA on this blog. I have written a few posts on the small cells blog but they seem to be dated as well. For anyone needing a quick refresher on LTE-U / LAA, please head over to IoTforAll or ShareTechNote. This post is not about the technology per se but the overall ecosystem with LTE-U / LAA (and even Multefire) being part of that.

Lets recap the market status quickly. T-Mobile US has already got LTE-U active and LAA was tested recently. SK Telecom achieved 1Gbps in LAA trials with Ericsson. AT&T has decided to skip the non-standard LTE-U and go to standards based LAA. MTN & Huawei have trialled LAA for in-building in South Africa. All these sound good and inspires confidence in the technology however some observations are worrying me.

Couple of years back when LTE-U idea was conceived, followed by LAA, the 5GHz channels were relatively empty. Recently I have started to see that they are all filling up.

Any malls, hotels, service stations or even big buildings I go to, they all seem to be occupied. While supplemental downlink channels are 20MHz each, the Wi-Fi channels could be 20MHz, 40MHz, 80MHz or even 160MHz.

On many occasions I had to switch off my Wi-Fi as the speeds were so poor (due to high number of active users) and go back to using 4G. How will it impact the supplemental downlink in LTE-U / LAA? How will it impact the Wi-Fi users?

On my smartphone, most days I get 30/40Mbps download speeds and it works perfectly fine for all my needs. The only reason we would need higher speeds is to do tethering and use laptops for work, listen to music, play games or watch videos. Most people I know or work with dont require gigabit speeds at the moment.

Once a user that is receiving high speeds data on their device using LTE-U / LAA creates a Wi-Fi hotspot, it may use the same 5GHz channels as the ones that the network is using for supplemental downlink. How do you manage this interference? I am looking forward to discussions on technical fora where users will be asking why their download speeds fall as soon as they switch Wi-Fi hotspot on.

The fact is that in non-dense areas (rural, sub-urban or even general built-up areas), operators do not have to worry about the network being overloaded and can use their licensed spectrum. Nobody is planning to deploy LTE-U / LAA in these areas. In dense and ultra-dense areas, there are many users, many Wi-Fi access points, ad-hoc Wi-Fi networks and many other sources of interference. In theory LTE-U / LAA can help significantly but as there are many sources of interference,its uncertain if it would be a win-win for everyone or just more interference for everyone to deal with.

Further reading:

Saturday, 10 December 2016

Free Apps for Field Testing

People who follow me on Twitter may have often noticed I put photos when I am doing surveys, field testing, debugging, etc. In the good old days we often had to carry a lot of different kind of specialised test equipment to do basic measurements. Nowadays a lot of these can be done with the help of free apps on Android phones. The best tool that can provide a great amount of info is Qualcomm's QXDM but its really expensive.

Here are a few tools that I use. If you have one that I havent listed below, please add it in comments.

The screen shot shows the main tools along with my favourite, SpeedTest. While I agree that Speedtest is not the most reliable approach to speed of your connection, I think its the most standard one being used.

WiFi Analyzer is another great app that can be used at home and other locations where people complain about not getting good WiFi speeds. I have been at locations where the 2.4GHz is absolutely packed with APs. 5GHz is also getting busier, though there are still a lot of free channels.

G-NetTrack Lite is a great tool to keep track of the cells you have been visiting. In case you are driving this can collect a lot of valuable info. The paid version, G-NetTrack Pro can collect the info in form of a map that can be used for offline viewing with the help of Google Earth.

I use LTE Discovery mainly for finding the band I am currently camped on. It would be great if a tool can give the exact frequency and earfcn but the band is good enough too. I was once in a situation where I could see two different cells but they had the same PCI. Only after using this, I figured out they were on different bands.

Finally, Network Cell Info Lite gives neighbour cells which can often be useful. I am not sure of these are the neighbours from System Info or from Measurement Control messages sent by network or just something like Detected cells that the phone sees around.

Pind and IPConfig are other tools that can come handy sometimes.

Are there any other tools that you like? Please share using comments.

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:

Monday, 26 September 2016

QoS in VoWiFi

Came across this presentation by Eir from last year's LTE Voice Summit.

As the summary of the above presentation says:
  • Turning on WMM (or WME) at access point provides significant protection for voice traffic against competing wireless data traffic
  • Turning on WMM at the client makes only a small difference where there are a small number of clients on the wireless LAN. This plus the “TCP Unfairness” problem means that it can be omitted.
  • All Home gateways support WMM but their firmware may need to be altered to prioritise on DSCP rather than layer two

As this Wikipedia entry explains:

Wireless Multimedia Extensions (WME), also known as Wi-Fi Multimedia (WMM), is a Wi-Fi Alliance interoperability certification, based on the IEEE 802.11e standard. It provides basic Quality of service (QoS) features to IEEE 802.11 networks. WMM prioritizes traffic according to four Access Categories (AC): voice (AC_VO), video (AC_VI), best effort (AC_BE), and background (AC_BK). However, it does not provide guaranteed throughput. It is suitable for well-defined applications that require QoS, such as Voice over IP (VoIP) on Wi-Fi phones (VoWLAN).

WMM replaces the Wi-Fi DCF distributed coordination function for CSMA/CA wireless frame transmission with Enhanced Distributed Coordination Function (EDCF). EDCF, according to version 1.1 of the WMM specifications by the Wi-Fi Alliance, defines Access Categories labels AC_VO, AC_VI, AC_BE, and AC_BK for the Enhanced Distributed Channel Access (EDCA) parameters that are used by a WMM-enabled station to control how long it sets its Transmission Opportunity (TXOP), according to the information transmitted by the access point to the station. It is implemented for wireless QoS between RF media.

This blog post describes how the QoS works in case of WMM.

Finally, this slide from Cisco shows how it will all fit together.

Further reading:

Tuesday, 4 August 2015

The Importance of License Exempt Frequency Bands

Some of you may be aware that I am also a Technical Programme Manager with the UK Spectrum Policy Forum. Recently we published a whitepaper that we had commissioned to Plum consulting on "Future use of Licence Exempt Radio Spectrum". It is an interested read not only for spectrum experts but also for people trying to understand the complex world of spectrum.

The report is very well written. Here are a few extracts in purple:

Licence exempt frequency bands are those that can be used by certain applications without the need for prior authorisation or an individual right of use. This does not mean that they are not subject to regulation – use must still comply with pre-defined technical rules to minimise the risk of interference. Most licence exempt bands are harmonised throughout Europe and are shared with other services or applications, such as radars or industrial, scientific and medical (ISM) equipment. Wi-Fi and Bluetooth are probably the most familiar examples of mass-market licence exempt wireless applications, but the bands support many other consumer devices, such as cordless phones, doorbells, car key fobs, central heating controllers, baby monitors and intruder alarms. Looking to the future, licence exempt bands are likely to be a key enabler of wireless machine to machine (M2M) communication applications.

Key benefits of licence exempt bands include:
  • For end-users:
    • Greater convenience and flexibility by avoiding the need for lengthy runs of cable in home and work environments
    • Ability to connect mobile devices to a fixed broadband network, reducing dependence on the mobile network and potentially saving costs both for the service provider and the end-user
    • Enhanced convenience, safety and security, e.g. through installation of low cost wireless alarm systems or ability to unlock vehicles remotely rather than fumbling with keys
  • For equipment vendors and operators:
    • Facilitating market entry – there is no need to acquire a licence to deploy a service
    • Enabling niche applications or services to be addressed quickly and cheaply using existing technology and spectrum – this has been particularly effective in serving new machine to machine (M2M) applications in areas such as health, transport and home automation.
    • Providing certainty about spectrum access – there is no need to compete or pay for spectrum access (though the collective nature of spectrum use means quality of service cannot be guaranteed)
    • The ability to extend the reach of fixed communication networks, by providing wireless local area connectivity in homes, businesses and at public traffic hotspots.
The two most notable drawbacks are the inability to guarantee quality of service and the more limited geographic range that is typically available (reflecting the lower power limits that apply to these bands). Licence exempt wireless applications cannot claim protection from interference arising from other users or radio services. They operate in shared frequency bands and must not themselves cause harmful interference to other radio services.

From a regulator’s perspective, licence exempt bands can be more problematic than licensed bands in terms of refarming spectrum, since it is difficult to prevent the continued deployment of legacy equipment in the bands or to monitor effectively their utilisation. There is also generally no control over numbers and / or location of devices, which can make sharing difficult and limits the amount of spectrum that can be used in this way.

In Europe, regulation of licence exempt bands is primarily dealt with at an international level by European institutions. Most bands are fully harmonised, whereby free circulation of devices that comply with the relevant standards is effectively mandated throughout the EU. However some bands are subject to “soft” harmonisation, where the frequency limits and technical characteristics are harmonised but adoption of the band is left to national administrations to decide.

A key recommendation, which I think would be very interesting and useful would be: Promote further international harmonisation of licence exempt bands, in particular the recently identified 870 – 876 MHz and 915 – 921 MHz band that are likely to be critical for supporting future M2M demand growth in Europe.

Note that a similar sub-1GHz band has been recommended for 5G for M2M/IoT. The advantage for low frequencies is that the coverage area is very large, suitable for devices with low date rates. Depending on how the final 5G would be positioned, it may well use the license exempt bands, similar to the LAA/LTE-U kind of approach maybe.

The whitepaper is embedded below and is available to download from here:

Saturday, 23 May 2015

The path from 4.5G to 5G

In the WiFi Global Congress last week, I heard this interesting talk from an ex-colleague who now works with Huawei. While there were a few interesting things, the one I want to highlight is 4.5G. The readers of this blog will remember that I introduced 4.5G back in June last year and followed it with another post in October when everyone else started using that term and making it complicated.

According to this presentation, 3GPP is looking to create a new brand from Release-13 that will supersede LTE-Advanced (LTE-A). Some of you may remember that the vendor/operator community tried this in the past by introducing LTE-B, LTE-C, etc. for the upcoming releases but they were slapped down by 3GPP. Huawei is calling this Release-13 as 4.5G but it would be re-branded based on what 3GPP comes up with.

Another interesting point are the data rates achieved in the labs, probably more than others. 10.32Gbps in sub-6GHz in a 200MHz bandwidth and 115.20Gbps using a 9.6GHz bandwidth in above 6GHz spectrum. The complete presentation as follows:

Another Huawei presentation that merits inclusion is the one from the last Cambridge Wireless Small Cells SIG event back in February by Egon Schulz. The presentation is embedded below but I want to highlight the different waveforms that being being looked at for 5G. In fact if someone has a list of the waveforms, please feel free to add it in comments

The above tweet from a recent IEEE event in Bangalore is another example of showing the research challenges in 5G, including the waveforms. The ones that I can obviously see from above is: FBMC, UFMC, GFDM, NOMA, SCMA, OFDM-opt, f-OFDM.

The presentation as follows:

Saturday, 16 May 2015

Smart Homes of the Future and Technologies

Saw the above picture recently on Twitter. While its great to see how connected our future homes and even cities would be, it would be interesting to see what technologies are used for connecting these devices.

Cambridge Wireless had a smart homes event last month, there were some interesting presentations that I have detailed below.

The first of these technologies discussed is LoRa. As can be seen, its billed as ultimate long range (10 mile) and low power (10 year battery lifetime) technology. It uses spread-spectrum making it robust to channel noise. Here is the presentation:

The next technology is Zigbee 3.0. According to Zigbee Alliance:

The new standard unifies ZigBee standards found in tens of millions of devices delivering benefits to consumers today. The ZigBee 3.0 standard enables communication and interoperability among devices for home automation, connected lighting, energy efficiency and other markets so more diverse, fully interoperable solutions can be delivered by product developers and service providers. All device types, commands, and functionality defined in current ZigBee PRO-based standards are available to developers in the new standard.

ZigBee 3.0 defines the widest range of device types including home automation, lighting, energy management, smart appliance, security, sensors, and health care monitoring products. It supports both easy-to-use DIY installations as well as professionally installed systems. Based on IEEE 802.15.4, which operates at 2.4 GHz (a frequency available for use around the world), ZigBee 3.0 uses ZigBee PRO networking to enable reliable communication in the smallest, lowest-power devices. Current ZigBee Certified products based on ZigBee Home Automation and ZigBee Light Link are interoperable with ZigBee 3.0. A complete list of standards that have been merged to create ZigBee 3.0 can be seen on the website at

“The ZigBee Alliance has always believed that true interoperability comes from standardization at all levels of the network, especially the application level which most closely touches the user,” said Tobin J. M. Richardson, President and CEO of the ZigBee Alliance. “Lessons learned by Alliance members when taking products to market around the world have allowed us to unify our application standards into a single standard. ZigBee 3.0 will allow product developers to take advantage of ZigBee’s unique features such as mesh networking and Green Power to deliver highly reliable, secure, low-power, low-cost solutions to any market.”

Finally, we have Bluetooth Smart mesh.

CSRmesh enables Bluetooth® low energy devices not only to receive and act upon messages, but also to repeat those messages to surrounding devices thus extending the range of Bluetooth Smart and turning it into a mesh network for the Internet of Things.

While the CW event was not able to discuss all possible technologies (and believe me there are loads of them), there are other popular contenders. Cellular IoT (CIoT) is one if them. I have blogged about the LTE Cat-0 here and 5G here.

A new IEEE Wi-Fi standard 802.11ah using the 900MHz band has been in works and will solve the need of connectivity for a large number of things over long distances. A typical 802.11ah access point could associate more than 8,000 devices within a range of 1 km, making it ideal for areas with a high concentration of things. The Wi-Fi Alliance is committed to getting this standard ratified soon. With this, Wi-Fi has the potential to become a ubiquitous standard for IoT. See also this article by Frank Rayal on this topic.

Finally, there is SIGFOX. According to their website:

SIGFOX uses a UNB (Ultra Narrow Band) based radio technology to connect devices to its global network. The use of UNB is key to providing a scalable, high-capacity network, with very low energy consumption, while maintaining a simple and easy to rollout star-based cell infrastructure.

The network operates in the globally available ISM bands (license-free frequency bands) and co-exists in these frequencies with other radio technologies, but without any risk of collisions or capacity problems. SIGFOX currently uses the most popular European ISM band on 868MHz (as defined by ETSI and CEPT) as well as the 902MHz in the USA (as defined by the FCC), depending on specific regional regulations.

Communication on SIGFOX is secured in many ways, including anti-replay, message scrambling, sequencing, etc. The most important aspect of transmission security is however that only the device vendors understand the actual data exchanged between the device and the IT systems. SIGFOX only acts as a transport channel, pushing the data towards the customer's IT system.

An important advantage provided by the use of the narrow band technology is the flexibility it offers in terms of antenna design. On the network infrastructure end it allows the use of small and simple antennas, but more importantly, it allows devices to use inexpensive and easily customizable antennas.

Sigfox is also working on project Mustang, a three-year effort to build a hybrid satellite/terrestrial IoT (internet of things) network. According to Rethink Research:

The all-French group also contains aerospace firm Airbus, research institute CEA-Leti and engineering business Sysmeca. The idea is to use Sigfox as the terrestrial data link, with satellite backhaul and connections to planes and boats provided by a low-earth orbit (LEO) satellite constellation.
The satellite link could be added to either the end devices or the base station, so that if a device was unable to connect to the terrestrial Sigfox network, it could fall back to the satellite.

While the power requirements for this would be prohibitive for ultra-low power, battery-operated devices, for those with a wired power supply and critical availability requirements (such as smart meters, alarms, oil tankers and rigs) the redundancy would be an asset. These devices may transmit small amounts of data but when they do need to communicate, the signal must be assured.

The Sigfox base station could be fitted with a satellite uplink as a primary uplink as well as a redundancy measure in some scenarios where terrestrial network reach cannot be achieved. With a three-year lifecycle, Mustang’s participants are looking to create a seamless global network, and note that the planned dual-mode terrestrial/satellite terminal will enable switching between the two channels in response to resource availability.

The group says that the development of this terminal modem chipset is a priority, with later optimization of the communication protocols being the next step before an application demonstration using an airplane.

The project adds that the full potential of the IoT can only be achieved by offering affordable mobile communications at a global scale and reach. Key to this is adapting existing networks, according to the group, which explains why Sigfox has been chosen – given that the company stresses the affordability of its system.

Well, there are a lots of options available. We just have to wait and see which ones work in what scenarios.

Sunday, 12 April 2015

LTE-Hetnet (LTE-H) a.k.a. LTE Wi-Fi Link Aggregation (LWA)

We have talked about the unlicensed LTE (LTE-U), re-branded as LTE-LAA many times on this blog and the 3G4G Small Cells blog. In fact some analysts have decided to call the current Rel-12 non-standardised Rel-12 version as LTE-U and the standardised version that would be available as part of Release-13 as LTE-LAA.

There is a lot of unease in the WiFi camp because LTE-LAA may hog the 5GHz spectrum that is available as license-exempt for use of Wi-Fi and other similar (future) technologies. Even though LAA may be more efficient as claimed by some vendors, it would reduce the usage for WiFi users in that particular spectrum.

As a result, some vendors have recently proposed LTE/WiFi Link Aggregation as a new feature in Release-13. Alcatel-Lucent, Ruckus Wireless and Qualcomm have all been promoting this. In fact Qualcomm has a pre-MWC teaser video on Youtube. The demo video is embedded as follows:

The Korean operator KT was also involved in demoing this in MWC along with Samsung and Qualcomm. They have termed this feature as LTE-Hetnet or LTE-H.

The Korean analyst firm Netmanias have more detailed technical info on this topic.

Link aggregation by LTE-H demonstrated at MWC 2015 (Source: Netmanias)

As can be seen the data is split/combined in PDCP layer. While this example above shows the practical implementation using C-RAN with Remote Radio Head (RRH) and BaseBand Unit (BBU) being used, the picture at the top shows LTE Anchor in eNodeB. There would be a need for an ideal backhaul to keep latency in the eNodeB to minimum when combining cellular and WiFi data.

Comparison of link level Carrier Aggregation technologies (Source: Netmanias)

The above table shows comparison between the 3 main techniques for increasing data rates through aggregation; CA, LTE-U/LAA and LTE-H/LWA. While CA has been part of 3GPP Release-10 and is available in more of less all new LTE devices, LTE-U and LTE-H is new and would need modifications in the network as well as in the devices. LTE-H would in the end provide similar benefits to LTE-U but is a safer option from devices and spectrum point of view and would be a more agreeable solution by everyone, including the WiFi community.

A final word; last year we wrote a whitepaper laying out our vision of what 4.5G is. I think we put it simply that in 4.5G, you can use WiFi and LTE at the same time. I think LTE-H fulfills that vision much better than other proposals.

Tuesday, 3 February 2015

5G: A 2020 Vision

I had the pleasure of speaking at the CW (Cambridge Wireless) event ‘5G: A Practical Approach’. It was a very interesting event with great speakers. Over the next few weeks, I will hopefully add the presentations from some of the other speakers too.

In fact before the presentation (below), I had a few discussions over the twitter to validate if people agree with my assumptions. For those who use twitter, maybe you may want to have a look at some of these below:

Anyway, here is the presentation.


Wednesday, 21 January 2015

Voice over WiFi (VoWiFi) technical details

VoWiFi is certainly a hot topic, thanks to the support of VoWiFi on iPhone 6. A presentation from LTE World Summit 2014 by Taqua on this topic has already crossed 13K views. In this post I intend to look at the different approaches for VoWiFi and throw in some technical details. I am by no means an expert so please feel free to add your input in the comments.

Anybody reading this post is not aware of S2a, S2b, Samog, TWAG, ePDG, etc. and what they are, please refer to our whitepaper on cellular and wi-fi integration here (section 3).

There are two approaches to VoWiFi, native client already in your device or an App that could be either downloaded from the app store or pre-installed. The UK operator '3' has an app known as ThreeInTouch. While on WiFi, this app can make and receive calls and texts. The only problem is that it does not handover an ongoing call from WiFi to cellular and and vice versa. Here are a few slides (slides 36-38) from them from a conference last year:

The other operators have a native client that can use Wi-Fi as the access network for voice calls as well as the data when the device is connected on the WLAN.

A simple architecture can be seen from the picture above. As can be seen, the device can connect to the network via a non-3GPP trusted wireless access network via the TWAG or via a non-3GPP untrusted wireless access network via ePDG. In the latter case, an IPSec tunnel would have to be established between the device and the ePDG. The SIM credentials would be used for authentication purposes so that an intruder cannot access ePDG and the core.

Now, I dont want to talk about VoLTE bearers establishment, etc. which I have already done here earlier. In order to establish S2a (trusted) and S2b (untrusted) connection, the AAA server selects an APN among those which are subscribed to in the HLR/HSS. The PDN-GW (generally referred to as PGW) dynamically assigns an IP address out of a pool of addresses which is associated with this APN. This UE IP address is used by the VoWiFi SIP UA (User Agent) as the contact information when registering to the SIP soft switch (which would typically be the operators IMS network).

If for any reason the SIP UA in the device is not able to use the SIM for authentication (needs ISIM?) then a username/password based authentication credentials can be used (SIP digest authentication).

Typically, there would be a seperate UA for VoLTE and VoWiFi. They would both be generally registering to the same IMS APN using different credentials and contact addresses. The IMS network can deal with multiple registrations from the same subscriber but from different IP addresses (see 3GPP TS 23.237 - 'IMS Service Continuity' for details).

Because of multiple UA's, a new element needs to be introduced in order to 'fork' the downstream media streams (RTP/RTCP packets) to different IP addresses over time.

3GPP has defined the Access Transfer Gateway (ATGW) which is controlled by the Access Transfer Control Function (ATCF); the ATCF interfaces to the IMS and Service Centralization and Continuity Application Server (SCC AS). All these are not shown in the picture above but is available in 3GPP TS 23.237. The IMS networks in use today as well as the one being deployed for VoLTE does not have ATGW/ATCF. As a result vendors have to come up with clever non-standardised solutions to solve the problem.

When there is a handover between 3GPP and non-3GPP networks, the UE IP address needs to be preserved. Solutions like MIP and IPSec have been used in the past but they are not flexible. The Release-12 solution of eSAMOG (see 3GPP TS 23.402) can be used but the solution requires changes in the UE. For the time being we will see proprietary solutions only but hopefully in future there would be standardised solutions available.

3GPP TS 23.234 describes more in detail the interworking of 3GPP based system and WLAN. Interested readers can refer to that for further insight.

Tuesday, 11 November 2014

New Spectrum Usage Paradigms for 5G

Sometime back I wrote a post that talked about Dynamic Spectrum Access (DSA) techniques for Small Cells and WiFi to work together in a fair way. The Small Cells would be using the ISM bands and Wi-Fi AP's would also be contending for the same spectrum. For those who may not know, this is commonly referred to as LTE-U but the correct term that is being used in standards is LA-LTE, see here for details.

IEEE Comsoc has just published a whitepaper that details how the spectrum should be handled in 5G to make sure of efficient utilisation. The whitepaper covers the following:

Chapter 2 – Introduction, the traditional approach of repurposing spectrum and allocating it to Cellular Wireless systems is reaching its limits, at least below the 6GHz threshold. For this reason, novel approaches are required which are detailed in the sequel of this White Paper.

Chapter 3 - Spectrum Scarcity - an Alternate View provides a generic view on the spectrum scarcity issue and discusses key technologies which may help to alleviate the problem, including Dynamic Spectrum Management, Cognitive Radios, Cognitive Networks, Relaying, etc. 

Chapter 4 – mmWave Communications in 5G addresses a first key solution. While spectrum opportunities are running out at below 6 GHz, an abundance of spectrum is available in mmWave bands and the related technology is becoming mature. This chapter addresses in particular the heterogeneous approach in which legacy wireless systems are operated jointly with mmWave systems which allows to combine the advantages of both technologies. 

Chapter 5 – Dynamic Spectrum Access and Cognitive Radio: A Current Snapshot gives a detailed overview on state-of-the-art dynamic spectrum sharing technology and related standards activities. The approach is indeed complementary to the upper mmWave approach, the idea focuses on identifying unused spectrum in time, space and frequency. This technology is expected to substantially improve the usage efficiency of spectrum, in particular below the 6GHz range. 

Chapter 6 – Licensed Shared Access (LSA) enables coordinated sharing of spectrum for a given time period, a given geographic area and a given spectrum band under a license agreement. In contract to sporadic usage of spectrum on a secondary basis, the LSA approach will guarantee Quality-of-Service levels to both Incumbents and Spectrum Licensees. Also, a clear business model is available through a straightforward license transfer from relevant incumbents to licensees operating a Cellular Wireless network in the concerned frequency bands. 

Chapter 7 – Radio Environment Map details a technology which allows to gather the relevant (radio) context information which feed related decision making engines in the Network Infrastructure and/or Mobile Equipment. Indeed, tools for acquiring context information is critical for next generation Wireless Communication systems, since they are expected to be highly versatile and to constantly adapt. 

Chapter 8 – D2DWRAN: A 5G Network Proposal based on IEEE 802.22 and TVWS discusses the efficient exploitation of TV White Space spectrum bands building on the available IEEE 802.22 standard. TV White Spaces are indeed located in highly appealing spectrum bands below 1 GHz with propagation characteristics that are perfectly suited to the need of Wireless Communication systems. 

Chapter 9 – Conclusion presents some final thoughts. 

The paper is embedded as follows:

Sunday, 19 October 2014

What is (pre-5G) 4.5G?

Before we look at what 4.5G is, lets look at what is not 4.5G. First and foremost, Carrier Aggregation is not 4.5G. Its the foundation for real 4G. I keep on showing this picture on Twitter

I am sure some people much be really bored by this picture of mine that I keep showing. LTE, rightly referred to as 3.9G or pre-4G by the South Korean and Japanese operators was the foundation of 'Real' 4G, a.k.a. LTE-Advanced. So who has been referring to LTE-A as 4.5G (and even 5G). Here you go:

So lets look at what 4.5G is.
Back in June, we published a whitepaper where we referred to 4.5G as LTE and WiFi working together. When we refer to LTE, it refers to LTE-A as well. The standards in Release-12 allow simultaneous use of LTE(-A) and WiFi with selected streams on WiFi and others on cellular.

Some people dont realise how much spectrum is available as part of 5GHz, hopefully the above picture will give an idea. This is exactly what has tempted the cellular community to come up with LTE-U (a.k.a LA-LTE, LAA)

In a recent event in London called 5G Huddle, Alcatel-Lucent presented their views on what 4.5G would mean. If you look at the slide above, it is quite a detailed view of what this intermediate step before 5G would be. Some tweets related to this discussion from 5G Huddle as follows:

Finally, in a recent GSMA event, Huawei used the term 4.5G to set out their vision and also propose a time-frame as follows:

While in Alcatel-Lucent slide, I could visualise 4.5G as our vision of LTE(-A) + WiFi + some more stuff, I am finding it difficult to visualise all the changes being proposed by Huawei. How are we going to see the peak rate of 10Gbps for example?

I have to mention that I have had companies that have told me that their vision of 5G is M2M and D2D so Huawei is is not very far from reality here.

We should keep in mind that this 4G, 4.5G and 5G are the terms we use to make the end users aware of what new cellular technology could do for them. Most of these people understand simple terms like speeds and latency. We may want to be careful what we tell them as we do not want to make things confusing, complicated and make false promises and not deliver on them.

xoxoxo Added on 2nd January 2015 oxoxox

Chinese vendor ZTE has said it plans to launch a ‘pre-5G’ testing base station in 2015, commercial use of which will be possible in 2016, following tests and adjustment. Here is what they think pre-5G means:

Sunday, 20 July 2014


Recently came across a presentation by Ericsson where they used the term LA-LTE. I asked a few colleagues if they knew or could guess what it means and they all drew blank. I have been blogging about Unlicensed LTE (a.k.a. LTE-U) on the Small Cells blog here. This is a re-branding of LTE-U

LA-LTE stands for 'Licensed Access' LTE. In fact the term that has now been adopted in a recent 3GPP workshop (details below) is Licensed Assisted Access (LAA).

Couple of months back I blogged in detail about LTE-U here. Since then, 3GPP held a workshop where some of the things I mentioned got officially discussed. In case you want to know more, details here. I have to mention that the operator community is quite split on whether this is a better approach or aggregating Wi-Fi with cellular a better approach.

The Wi-Fi community on the other hand is unhappy with this approach. If cellular operators start using their spectrum than it means less spectrum for them to use. I wrote a post on the usage of Dynamic Spectrum Access (DSA) Techniques that would be used in such cases to make sure that Wi-Fi and cellular usage does not happen at the same time, leading to interference.

Here is a presentation from the LTE-U workshop on Use cases and scenarios, not very detailed though.

Finally, the summary presentation of the workshop. As it says on the final slide "The current SI proposal focuses on carrier aggregation operations and uses the acronym LAA (Licensed Assisted Access)", you would be seeing more of LAA.

Friday, 4 July 2014

Cell capacity and Opportunistic Use of Unlicensed and Shared Spectrum

One very interesting presentation from the LTE World Summit was about Improving the cell capacity by using unlicensed and shared spectrum opportunistically. Kamran Etemad is a senior advisor to FCC & UCMP and even though he was presenting this in his personal capacity, it reflected some interesting views that are quite prevalent in the USA.

If you don't know about Dynamic Spectrum Access Schemes, I wrote a post on the Small Cells blog here. The slide above is quite interesting as it shows the possibility of a 'Generalized' Carrier Aggregation in 3GPP Release-13. Personally, we believe that LTE + WiFi working together will be far more successful than LTE + LTE-U (unlicensed). As the blog readers would be aware, we have been pushing our vision of LTE + Wi-Fi working together; which we are calling as 4.5G. In case if you have not seen, our whitepaper is here.

The presentation is embedded below for reference:

Monday, 30 June 2014

4.5G: Integration of LTE and Wi-Fi networks

With LTE-A getting ready to meet the IMT-Advanced requirements and fulfilling the role of promised '4G', we believe the next phase of evolution before 5G will be successful interworking of LTE and Wi-Fi networks.

This whitepaper (embedded below) explores this feature, we call 4.5G, in detail.

Understanding WLAN offload in cellular networks by Anritsu

We are very thankful to Anritsu for kindly sponsoring this whitepaper. They have their own whitepaper on this topic which is also worth a read, available here.

Let us know what you think about this.

Friday, 27 June 2014

Voice over WiFi (VoWiFi)

One of the changes that I have noticed in the last year is that some of the operators who have been opposed to WiFi in the past have not only embraced it but are now trying to monopolise the same WiFi spectrum they billed as interference prone. Personally, I think the future of Wi-Fi is not just offloading but also working together with LTE. We are billing this as 4.5G and have recently produced a whitepaper, available here.

There has been a flurry of activity on Voice over Wi-Fi in the last few months. Recently the UK operators '3' and EE announced that they are both allowing WiFi calling and SMS. While '3' customers will have to use an OTT app for the time being, EE customers will experience this seamlessly.

I heard Taqua in the recent LTE World Summit talking about their solution and have offered to share their slides (embedded below). It was interesting to find out while having a discussion with them that their solution supports 'hand-in' and 'hand-out'. This takes away a major advantage that Small Cells offered, seamless roaming. Anyway, feel free to let me know of you have any opinion on this topic

Thursday, 26 June 2014

LTE-Broadcast: Reality check

When I wrote my blog post about why the 'Cellular Broadcast may fail again' for the Cisco SP Mobility blog, I did not realise that this would become so popular and there would be so many people writing to me to tell me why and how my assumptions are wrong and how they plan to succeed. I have not yet received a successful reasoning on why people disagree with my article and where I am wrong.

In the Video Over LTE Summit just concluded, I did not get a chance to see all the LTE-B presentations but the ones that I saw, were not convincing enough, except for one by Erol Hepsaydir, of '3' UK, that I explain in the end.

Here is my presentation from that event:

The conclusion is not self-explanatory so here it is in my own words.

I am not opposed to the operators trying LTE-B out. I wish more operators do try and hopefully we can have a model where the technology can succeed. When operators succeed in a new technology, it benefits the whole mobile ecosystem directly or indirectly. The operators have to be prepared that they may not see any return. This should not discourage them because the learnings from this may benefit in something else. The customer and their loyalty is more important. We should try and provide them with a value addition rather than think of this as a new source of revenue. People are not interested in watching the same stuff they watch on the terrestrial TV on their small devices; unique and maybe tailored content would help. Finally, don't make the billing model too complex so the users shy away from trying this new technology.

The final presentation of the event was delivered by Erol Hepsaydir of the UK operator '3'. He said that from their point of view, they are trying to have eMBMS to create additional capacity in the network. If they know that many people watch news on different apps and websites, they can offer this as a free service over broadcast. What this means is that they have gained customer loyalty and also free up the capacity for other users who are doing other data related activities. I think this is a very clever approach. He did mention though that they are only in the simulation stages and have not tried it out practically. 

Wednesday, 21 May 2014

Connected and Autonomous Car Revolution

Last week we had the Automotive and Transport SIG event in Cambridge Wireless. There is already some good writeup on that event here and here. In this post my interest in looking at the technologies discussed.

R&S (who were the sponsors) gave their introduction presentation quite well highlighting the need and approaches for the connected car. He also introduced the IEEE 802.11p to the group.

As per Wikipedia, "IEEE 802.11p is an approved amendment to the IEEE 802.11 standard to add wireless access in vehicular environments (WAVE), a vehicular communication system. It defines enhancements to 802.11 (the basis of products marketed as Wi-Fi) required to support Intelligent Transportation Systems (ITS) applications. This includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed ITS band of 5.9 GHz (5.85-5.925 GHz). IEEE 1609 is a higher layer standard based on the IEEE 802.11p."

Back in December, Dr. Paul Martin did an equally useful presentation in the Mobile Broadband SIG and his presentation is equally relevant here as he introduced the different terms live V2X, V2i, V2V, V2P, etc. I have embedded his presentation below:

Roger Lanctot from Strategy Analytics, gave us some interesting facts and figures. Being based in the US, he was able to give us the view of both US as well as Europe. According to him, “LTE is the greatest source of change in value proposition and user experience for the customer and car maker. Bluetooth, Wi-Fi, NFC and satellite connectivity are all playing a role, but LTE deployment is the biggest wave sweeping the connected car, creating opportunities for new technologies and applications.” His officially released presentation is embedded below (which is much smaller than his presentation on that day.

There were also interesting presentations that I have not embedded but other may find useful. One was from Mike Short, VP of Telefonica and the other was from Dr. Ireri Ibarra of MIRA.

The final presentation by Martin Green of Visteon highlighted some interesting discussions regarding handovers that may be required when the vehicle (and the passengers inside) is moving between different access networks. I for one believe that this will not be an issue as there may be ways to work the priorities of access networks out. Anyway, his presentation included some useful nuggets and its embedded below: