Defining HetNets (Heterogeneous Networks)

Recently added a video/presentation looking at 2 different definitions of Heterogeneous Networks (HetNets). Presentation with video embedded below. If you like to jump to video directly, here is the link.

The 2 definitions of Heterogeneous Networks (HetNets) from 3G4G

Related post:

• Tutorial: An Introduction to Macrocells & Small Cells

Small Cell Forum workshop on 5G

I was having a twitter discussion earlier today as to whether 2G/3G should be switched off to make room for the more efficient 4G/4G+. While I agree with regards to the efficiency of 4G/4G+, there is still plenty of room for existing technologies, including 2G for a long time. 

While 5G is great and as can be seen in the picture above, a very optimistic picture has been painted with regards to LTE/5G.

Small cell forum recently held a workshop on 5G in Rome. Though it doesn't say explicitly, I am assuming the focus was Small Cells and 5G. It wouldn't be surprising as most of mmWave deployments would be comparatively small as compared to macrocells today.

“All of 5G looks a lot like a small cell” - Matt Beal, Vodafone Director of Innovation and Architecture at #SCWS2016 https://t.co/RGSC6aSTLF

— Zahid Ghadialy (@zahidtg) August 28, 2016

I like this picture below as it shows that there are practical problems to solve today then worry about the 5G deployments of 2020. Having said that, the mobile community has to start preparing for it now to be ready by early 2020's  

Huawei had another interesting concept of how 5G HetNets will look

Nokia suggested that the lessons learned from Small Cells will help vendors with 5G deployments.

You can see all the presentations available here.

If you found something very interesting, please share in comments.

HetNets On The Bus

Earlier in March, I helped organise 'The Gigabit Train' seminar'. The intention was to look at the connectivity options inside the trains and its monetisation. While connectivity in the trains is challenging, thinking back about it, due to a predictable route it can be sometimes easy to deploy. It could be more of a challenge for cars and buses that go through unpredictable routes and conditions.

I also discussed the "Vehicular CrowdCell" or "Vehicular Small Cell" concept here to look at some advantages of such a solution option.

Some of you may be aware that I recently joined Parallel Wireless. We were selected by M1 Limited, Singapore’s most vibrant and dynamic communications company, to support its WiFi-On-The-Go service as a part of the HetNet trial.

This is the architecture of the On-Bus Hetnet. Some of you would find it self-explanatory.

The mobile operators in Singapore are looking for innovative technologies to address spectrum scarcity as subscriber demand is growing rapidly with smartphone penetration reaching 130 devices per 100 people. Maximizing utilization of the spectrum and easing network congestion in areas with heavy human traffic is necessary to meet Infocomm Development Authority of Singapore (iDA) vision of connecting the whole nation as a part of world’s-first Smart Nation initiative.

Real-time HetNet orchestration and traffic prioritization is made possible by HetNet Gateway (HNG). All bus riders receive seamless, high throughput connectivity from an on-bus multi-mode LTE/Wi-Fi Converged Wireless System (CWS) small cell with integrated backhaul including licensed assisted backhaul.  By enabling carrier aggregation for backhaul, the end user throughput can be increased 10 times (up to 300 Mbps) allowing transit passengers to enjoy multimedia content without buffering.

Here is a presentation that gives the complete story:

Some questions on this demo from Linkedin:

Q: Does seamless handover are available with no drop in data throughput through out the travel route of Bus? 
A: Yes, handover is seamless, no dropped data or voice calls. This was one of the iDA trial requirements. We can do seamless VoLTE to VoWiFi handover and back.

Q: What is the maximum data rates does the system accommodate for all seamless data transfers? Does the system support motion video play from N/W. If so of what bandwidth and data rates? 4. How many users does the system support and what data rates?
A: It will depend on the backhaul. We can increase backhaul capacity with CA on 4G + to 300 Mbps shared bandwidth.

Q: This seems to be a relay device ( a femto or pico grade small cell with UE backhaul). an their innovative hetnet gateway for traffic engineering ( LBS support ). 
A: Our in-vehicle unit is a Small cell (LTE/Wi-Fi for access) with any backhaul incl UE backhaul. The HetNet Gateway, in addition to performing 3G, 4G, WI-Fi gateway functionality and real-time SON with ICIC, will also do the traffic engineering.

And demo from inside the bus:


Further reading:

• Parallel Wireless Selected by M1 to Support Smart Nation Trial

LTE-A, Hetnets and Phase Timing

I was going through my old presentations looking at frequency and phase requirements for LTE-A and HetNets. The slide above is some years old but it does summarise the requirements well. There is also an interview by Martin Kingston & Andy Sutton of EE on this topic which is available here. I would think that with 5G latencies often quoted as less than 1ms (but in practice it may be up to 10ms) would have very critical frequency and phase timing requirements.

ThinkSmallCell recently held a webinar on this topic. The write-up is available here and slides/video is embedded below. Here is something I found interesting:

In the past, a central Grand Master supplied a common signal that was hardwired throughout the network. Today, we now see distributed master clocks appearing almost everywhere. Typical requirements are for 50ppb frequency and 1.5us phase timing over the air, driven from 16ppb and 1.1us into the base station.

Frequency sync requires a Primary Reference Clock (PRC), whereas Timing sync requires a Primary Reference Time Clock (PRTC). The latter must come from a satellite GNSS source, such as GPS, and be traceable to Universal Co-ordinated Time (UTC).

The end-to-end Inter-Cell time error budget of 1.5us (1500nanoseconds) is split into three parts:

• A time source, with an error of up to 100n
• The transmission network, with up to 1000ns
• The small cell (eNodeB), with up to 400ns

The transmission network may have up to 10 boundary clocks with a combined total of 500ns error. The remaining allowance is split equally between dynamic time errors and network asymmetry. It is especially important that packets travelling in each direction (uplink/downlink) incur similar amounts of delay variation – if the time taken to send and receive packets varies differently, then phase timing errors would mount up rapidly.

It is this asymmetry of packet delay variation which is the biggest problem with engineering phase timing throughout a large network.

The ITU has defined two different time profile standards related to transmitting the phase sync signal.

G.8275.1, which relies on full on-path support. Each node in the backhaul transmission network must be fully aware of the phase timing component and actively support its transmission. Each router or node would have its own boundary clock that synchronises and re-generates the timebase locally. This may be feasible for new product but would otherwise require replacement or upgrade for existing routers and backhaul transmission equipment.

G.8275.2 was recently consented and only requires partial on-path support. One or more boundary clocks are installed at the most effective points in the backhaul path, with many legacy routers/nodes being unaware of the special importance of the PTP packets.

It is crucial to take into account the existing technical infrastructure and also cost for deployment. As part of this effort, it is critical to engineer the network so that asymmetry correction can be considered.

In cases where full on path support is deployed, the mitigation of uplink versus downlink asymmetries are extremely important and usually requires a manual calibration of each link which is extremely costly.

Here are the slides with Video in the end. Video can also be directly viewed on Youtube here.

*** Edited 11/04/16 - 10.30 ***

RTT has just published an article on related topic titled 'A second look at time', available here.

Wireless densification via HetNet orchestration

According to a whitepaper that was published late last year by ThinkSmallCell:

There are commonly thought to be three ways to densify wireless traffic capacity:
1. More spectrum (expensive, limited)
2. More spectrally efficiency (e.g. LTE rather than 2G)
3. More spatial reuse (i.e. small cells)
But there is also a fourth aspect which can deliver significant additional benefit
4. Orchestration and tighter control. (e.g. SON (Self Organising Networks), traffic steering/shaping across and between all available wireless resources)

This has been a key factor driving replacement of outdated macrocells with “Single RAN” basestation equipment that supports all generations of radio interface. These specifically address (1) and (2) above. What’s needed next is investment in tools and equipment that provides similar flexibility for (3) and (4), scaling to cope with an influx of small cells and introducing real-time management and co-ordination across all available wireless technologies, both cellular and Wi-Fi.

While we dont generally hear a lot about SON nowadays, I know most of the vendors have implemented some or the other aspects of SON in their equipment. Orchestration can definitely have a much bigger impact than SON by itself on the densification.

In 5G, we talk about 'edgeless cells', 'no-edge networks', etc. Orchestration of the network will have a big part to play in this too.

Anyway, here is the whitepaper embedded below and available to download from Slideshare

Interference cancellation in high density small cells deployment

I looked at some 3GPP Release-12 small cells enhancements in an earlier blog post here. David Chambers, ThinkSmallCell has also published a post on 3GPP small cells enhancements in Release-12 and Release-13 which is available here.

In a recent NTT Docomo technical journal, there is an article that focuses on Interference suppression and cancellation techniques that have been introduced as part of 3GPP Release-12. These techniques can be used in conjunction with high density small cells Hetnet deployment. The article is embedded below.

Connectivity in the stadiums

I have recently been observing a lots of discussions around connectivity in the stadiums. I have used this picture above a few times to show different solutions available in different situations. You can see that in theory Wi-Fi, DAS, Micro and Pico would all be suitable for the connectivity in stadiums. In practice this is generally limited to DAS and Wi-Fi.

ThinkSmallCell have recently written an article on the stadium Wi-Fi experience of The Cloud here. Some very interesting choices were taken to keep things simple:

For the main stadium bowl, The Cloud designed for 50% concurrent access for the maximum 30,000 crowd, connecting 80 Wi-Fi access points using 1km of fibre and 9km of CAT6 ethernet cable.

Each access point can handle up to 250 concurrent users. Tightly focussed beams were used to segregate seating blocks, splitting these into distinct coverage sectors.

To simplify the design, the older 802.11b standard wasn't used/supported, VoIP was blocked and a maximum of 3 SSIDs assigned. Unlike a cellular system, there's no handoff as you move around the stadium – you'd need to reconnect and create another session. During peak usage, almost everyone is sitting down rather than moving about (if you ignore those jumping up and down on their seats).

Both Wi-Fi spectrum bands at 2.4GHz and 5GHz were used, with devices capable of the higher frequency prioritised to use it. 56% of clients used the 5GHz band, which has much more spectrum and many more channels available. The different propagation characteristics mean there are different coverage footprints, so planners are actually designing two networks rather than one.

The side lobes on the 5GHz coverage footprint were massive, limiting the number of Wi-Fi access points that could be deployed.

You can read the complete article on the ThinkSmallCell website here.

A question some people often ask is why bother with connectivity in the stadiums. There are many reasons and personally, I would rather have connectivity than don't, even if I am not going to use it.

Real Wireless has done substantial amount of work in this area and a slide from their recent presentation discusses the benefits for various parties very well. You can read their opinion on this topic on their website here.

No discussion on Stadium connectivity would be complete without mentioning the US operator AT&T. They regularly publish statistics and details of connectivity in various sports venues on their website here. A recent report from their new site on DAS connectivity in various stadiums as follows:

• So far this season, there have been 119 pro football games and 214 college football games played across more than 75 different venues where we provide in-venue coverage via Distributed Antenna Systems (DAS). 
• In total, across these 333 games our customers have used more than 104.9 Terabytes of mobile data on our in-venue cellular networks. That’s the same as 104,913 Gigabytes. Or more simply put, it is equivalent to more than 300M social media posts with photos. 
• At this point in the year, pro football fans are edging college fans in average data usage per game by a 342GB to 293GB margin. Or a difference equivalent to about 140K more social media posts with photos per game on average.

Another recent report from the AT&T part in San Francisco where both Wi-Fi and DAS are present as follows:

Here are some of the record-breaking numbers we saw on our venue-specific mobile network at AT&T Park from the Giants’ three home games during the World Series:

• Fans used more than 477GB of data on the AT&T cellular network during the game on 10/25. This is equivalent to more than 1.36M social media post with photos.
  • This marked the highest single game total for cellular data usage at AT&T Park in ballpark history.

• Fans used an average of approximately 447GB of data per game over the weekend on the AT&T cellular network. This is equivalent to more than 1.27M social media post with photos.
  • It’s an increase of approximately 29% in cellular data usage compared to the average game during the League Championship series vs. St. Louis.
  • It’s an increase of approximately 109% in cellular data usage compared to the average game during the final home series of the regular season vs. San Diego (9/25-9/28).
• The peak hour of data usage during three home games was on 10/25 was from 5-6pm PT, the hour in which the first pitch occurred. In this hour more than 83GB of data crossed our venue-specific cellular network.

• On our AT&T Wi-Fi network we saw more than 1,626GB of data move across our network during the game on 10/25.
  • This is the highest single game Wi-Fi total in the history of AT&T Park.
  • 1,626GB is equivalent to more than 4.65M social media post with photos.
  • This showed an increase in Wi-Fi usage of approximately 302% compared to the average game during the 2012 World Series.
  • This showed an increase in Wi-Fi usage of approximately 163% compared to the average 2014 regular season game at AT&T Park.
  • This showed an increase in Wi-Fi usage of approximately 29% compared to the average game of the League Championship series vs. St. Louis.

• The collective data usage equaled approximately 2.1TB of data across both our cellular and Wi-Fi networks at AT&T Park during the game on 10/25.
  • This marked the highest single game total for collective data usage (cellular and Wi-Fi) in AT&T Park history.
  • 2.1TB is equivalent to more than 6M social media post with photos.

Note: All cellular data is specific to only AT&T customers using the DAS network at AT&T Park.

AT&T DAS guru Paula Doublin was one of the most memorable speakers at this year’s HetNet Expo. The company’s AVP for antenna solutions, DAS and small cells did not shy away from questions about AT&T’s budget for heterogeneous networks, nor did she sugar coat the outlook for small cell deployments. A video of her presentation is embedded below and a writeup is available on RCR Wireless website here.




See Also:

• Case Study: Deployment scenarios with DAS, RRH, Small Cells and Wi-Fi
• HetNet Strategies with Oi Brazil

HetNet Strategies with Oi Brazil

Brazil has been in limelight since the beginning of the year. Initially, the focus was on how the FIFA World Cup may fail but later on for the way everything came together at the last minute and everything worked. From a technology point of view, WiFi was a big saviour in the stadiums, allowing good connectivity for everyone wishing to add the things they liked on social networks as soon as they can.

An example was this chart tweeted by Ruckus Wireless to proudly show what their achievement was with stadium WiFi.

Recently, Maravedis-rethink conducted a webinar with the Brazilian operator Oi, regarding their HetNet strategies. The video for the relevant part is embedded in the end. Two slides caught my attention. The first was about the different technologies and their concerns (above). For example for a HetNet to be successful, all components should synchronised and have a strict time accuracy requirements. The Backhaul & Fronthaul requirements are equally interesting for different cases.

The second interesting slide is the final one where they have their wish list to what they would like to do in near-term and long-term. WiFi features in all the scenarios except for the rural case (as expected). Anyway, here is the video:



You can download the slides from Slideshare here.

New types of HetNet's Cell coordination

Came across this HetNet Infographic from Ericsson here. They are proposing something interesting as can be seen in the picture above. From the infographic:

Macro for downlink, micro for uplink
In the imbalance area, the downlink signal from the macro is the strongest, because it transmits at a much higher power, whereas the uplink signal from the pico node is much stronger, because it is closer. This provides the user with significantly higher uplink speeds than would be possible with macro coverage alone.

So if we have a macro with an overlay of small cells then the Macro can be used for DL and Small Cells for UL. This scheme is a counterintuitive to what I would have thought. Since there is a higher requirement in DL as opposed to UL, the uplink could be received by Macro and the DL could be sent from pico node. The macro also has bigger antennas and can process weak signals from the UE.



Ericsson and the South Korean operator, SK Telecom recently also demonstrated 'Elastic Cell'. As per Telecom TV:

The telco has confirmed that Elastic Cell technology is based on the 3GPP Release 11 CoMP specification, but with improved scheduling, energy efficiency, and cost efficiency. SK Telecom says it has applied downlink CoMP since early 2012 and uplink CoMP in April 2014, and both technologies are proprietary technology. Because coordination between networks will still be very important in 5G technologies, SK Telecom expects that Elastic Cell will become a key enabler for 5G.

Another similar approach that is proposed by NTT Docomo is the 'Phantom Cell' concept as described here. Their proposal is to separate control and user planes. Macro used for signalling (C-plane) and Small cells in higher frequencies for data (U-plane)

Finally, we also have the SK Telecom's SUPER Cell concept and blogged here. There is a lot of cell splitting in this but again we have the main frequency (lower) being able to do both control and data while the higher frequency is only to do data. Sounds a bit like the Phantom Cell and 'New Carrier Type' as blogged here before.

Are there any other types of cell coordination being discussed. Do you have any opinion on them? Feel free to add comments.

X2: The necessity for Interoperability and Interference management in HetNets

Recently I wrote an article in the TMN magazine here about HetNet co-ordination. One important point that I mentioned here (and in several of the trainings that I do) is that X2 can be quite a useful interface, especially when you want to manage Interference between just macro cells or between different types of cells, as in HetNet environment. From the TMN article:

The initial deployments of LTE did not pay too much emphasis on X2 interface being present. Inter-operability was another issue for which X2 didn’t work very well. One of the major benefits of having an X2 interface is that different base stations or eNodeB’s (hereafter referred to as just eNB’s) can talk to each other and coordinate to make sure interference is kept at the minimum, especially on the cell edges. The Macro-cell’s had the provision for the X2 interface from the beginning, which formed the basis for Inter-Cell Interference Coordination (ICIC). Initially, the Small-cell’s didn’t have a facility for an X2 interface amongst them or with the Macro-cell. The support of X2 for Small-cell’s was added in 3GPP Release-10 and 3GPP Relese-11 (hereafter referred to as just Release-10 and Release-11) as seen in the picture. X2 for Small-cell’s is crucial for Interference management in HetNets.

The Small Cell Forum just published a whitepaper called "X2 interoperability in multi-vendor X2 HetNets". This paper is quite interesting with just the right amount of details. In their own words:

A key area of standardization needed to support small cells relates to the procedures to assist co-ordination with macrocells over LTE’s ‘X2’ interface. This document surveys standards currently in place to support frequency domain interference coordination,time domain interference coordination, mobility robustness and mobility load balancing. 

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

Small Cell Forum Release 4: X2 Interoperability from Zahid Ghadialy

HetNet and LTE Trends and Challenges

Metrocells and C-RAN has been a frequent area of discussion on this blog. A good post about Metrocells is available here and about C-RAN is available here and here.

I found a small and useful presentation in my collection that highlights the trends, opportunities and challenges with the HetNets. The presentation is embedded below:

HetNet and LTE trends from 3G4G Blogs

Optimizing Small Cells and the HetNets

Came across a whitepaper from JDSU, not so new but its got some interesting stuff. In an earlier post here, we saw the challenges for small cells deployment, the picture above shows another view.

Another interesting item is adding intelligence to small cells. This can mainly help by reducing the traffic back to the core. This also relies on predicting the user behaviour which could be a challenge in it self. There is a lot more interesting stuff in the paper, which is embedded below:

JDSU: Optimizing Small Cells and the Heterogeneous Network (HetNet) from Zahid Ghadialy

Super Macros and HetNets

The other day I read the following on Light Reading:

UK operator EE wants to turn its existing macro cell sites into "super macros," according to Andy Sutton, the carrier's principal network architect, speaking at the recent Base Station conference in London.

EE 's plan to super size its macro cell sites fits in to a broader Heterogeneous Network (HetNet) strategy for adding capacity and extending coverage. The operator rolled out the first LTE network in the UK last year, and has now covered 55 percent of the UK population and has 1 million 4G customers.

"Super macro is the first step toward building a HetNet,” said Sutton. “Evolving the macro is the most cost-optimized way to adding capacity into our networks."

But what makes a macro super?

According to Sutton, a super macro would typically have multiple radio access technologies (RAT), three-to-six base station sectors, and operate in multiple frequency bands using carrier aggregation techniques. It could be a standalone base station or a hub for subtended, smaller micro cells. He added that infrastructure sharing is vital to the strategy as well.

Once the operator has sufficiently beefed up its macro cell sites, then it can look to smaller cells to be deployed indoors and outdoors in hotspots or cell edge locations. Sutton described a small cell deployment as an "underlay" to the super macro.

The term super macro isn't exactly new, but the fact that operators are talking about it now indicates just how much more they are looking to do with their existing radio access network (RAN) infrastructure before introducing new small cells or while planning a small cell deployment.

"Within the super macro concept, there's quite a lot operators can do to improve performance," says Heavy Reading senior analyst Gabriel Brown.

Along with adding sectors, using more spectrum bands, or employing carrier aggregation, Brown also includes in the super macro concept using 4x4 and 8x8 MIMO, active antenna systems, vertical sectorization, or beamforming.

The advantage of improving macro sites is that many of the basic elements that go into the total cost of ownership of a cell site are already in place, such as power, real estate rental, and backhaul, according to Brown.

I remember the folks from Ericsson mentioning about Super macros but I had not given any thoughts to it. Well, I went back to see what they have been talking about and found this:

Since it was not very clear, I found some additional information from an NGMN presentation as follows:

Building a Sustainable HetNet - Telus, Canada

Came across this interesting presentation from the LTE World Summit 2013, one from Telus in Canada. The presentation is embedded below but here are couple of things that caught my attention:

One of the issues which is now becoming universal is the need to negotiate with the municipalities and local councils for the right to lamp posts and other street furniture. I blogged this earlier as well with regards to a presentation by EE here. This also encourages for a third party to provide small cells hosting as a service (SCaaS)

Interference in 3G Hetnets in case of shared carrier

We had a discussion earlier on 'dedicated v/s shared' carrier here. This post is just re-iterating the fact that while in case of LTE, there are advanced techniques like eICIC to manage interference (see 3G4G blog here), in case of 3G there are no standard techniques to manage the interference in case of shared carrier.

A recent presentation from ZTE in one of the conferences explains this point further that has been reproduced below for reference:

LTE-A Metrocells to boost the data capacity capabilities in HetNet base stations

From Business Weekly:

A transatlantic technology collaboration between Cambridge Consultants in the UK and Florida-based Airspan Networks is set to enhance speed and capacity over the transformational LTE (long term evolution) platform.

The partners have unveiled an LTE-Advanced metrocell boost for mobile broadband; 4G LTE, is a standard for wireless communication of high-speed data for mobile phones and data terminals.

Cambridge Consultants has collaborated with Airspan, a leading vendor of LTE small cells and broadband wireless products and solutions, to boost the data capacity capabilities of the US company’s heterogenous network (HetNet) base stations.