Tutorial: An Introduction to Macrocells & Small Cells

I have been meaning to create a video tutorial on Small Cells for a long time. The problem is that its not as easy as most people may think. To explain small cells concepts, its necessary to explain macrocell, C-RAN & DAS. This is what I have attempted to do in this presentation.

The slides are embedded below and can be downloaded from Slideshare. The video is embedded on slideshare presentation but if you prefer, the direct Youtube link is here.

Please note that this video is for guidance only. Many vendors & operators use their own definition which may not agree to mine. In the end, we are all correct 😉

Antennas for Small Cells and C-RAN

While a special antenna is not required for Small Cell deployment in general, they do require the right kind of antennas to make sure the original purpose of deployment is achieved.

Specifications for base-station antennas for use with small cells developed by NTT DOCOMO are shown in the picture above. The following is from the NTT Docomo Technical Journal:

These antennas feature dual polarization and can be shared among the 1.5 GHz and 1.7 GHz frequency bands. A separately developed compact duplexer is installed between the SRE and antenna to separate and combine signals of these frequency bands. The compact configuration of these antennas simplifies their installation.

When planning a service area by placing small cells next to each other, deterioration in signal quality due to interference between small cells is an issue of concern. To resolve this issue, downward tilting in the vertical plane is effective to reduce the interference caused by that antenna’s signals on adjacent cells while also to raise the receive level within the antenna’s own cell. The end result is improved throughput. The following summarizes the features of three types of antennas developed by NTT DOCOMO taking interference reduction and diverse installation environments into account.

1) Rod Antenna (Two Types): Having an omnidirectional radiation pattern in the horizontal plane, this type of antenna is installed on the wall or ceiling of a building to form a service area in its periphery. Two types of rod antennas have been developed: one with tilting for an interference-reduction effect and the other with no tilting for a compact configuration. The rod antenna with tilting consists of multiple vertically aligned antenna elements, the amplitude and phase of each of which is adjusted to produce an electrical tilt. The tilt angle, however, is predetermined.

2) Plane Antenna: This type of antenna has high gain while having a unidirectional radiation pattern making it applicable to installation on high places like building roofs to form a service area in a spot-like manner. A plane antenna can be given a mechanical tilt with a metal fixture to reduce interference.

Interested readers can download the article from here.

I also posted an article on the 3G4G blog titled 'Antenna evolution: From 4G to 5G'. The presentation by Kathrein provides more details on Small Cells and mmWave antennas. Why mmWave? Because most of the industry thinks that mmWave 5G will be small cells.

“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

The relevant part is embedded below

As always, comments, insights and suggestions welcome.

Current-State and Future of In-Building Tech

From a talk presented by John K. Bramfeld (@johnbramfeld) in Wireless Training Seminar & Networking Event - DASpedia West. The talk was 60 minutes but there are just 26 slides; most of the info was in the commentary. Anyway, it is an interesting presentation.

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.

Airvana's OneCell™ with C-RAN and Super-cell

Airvana recently announced its OneCell™ system was named the winner in the “In-Building Wireless – Small Cell, Wi-Fi, LAN” category of CTIA’s annual Emerging Technology (E-Tech) Awards competition. I remember back in June, it received a lot of praise for this product. So what exactly is so unique in this OneCell™.

From their press release back in June:

Based on cloud RAN principles, the OneCell system consists of a Baseband Controller and multiple Radio Points. Together they form a single "super" cell that delivers consistently high quality LTE service across indoor spaces ranging from 50,000 to 1,000,000 square feet without handovers or inter-cell interference issues. OneCell supports plug-and-play deployment over standard Ethernet cabling and switches, eliminating the need for proprietary networks or expensive optical links. Further, its unique small cell cloud RAN architecture dramatically simplifies radio frequency planning and integration with wireless macro networks.

There is a mention of C-RAN (though I have had discussion where this claims have been disputed), Super-cell and is pitched towards enterprises.

Airvana's website has a good picture explaining how a super-cell gets rid of interference on cell edges as all the cells work together as a single large cell.

In fact the scheduler can cleverly assign the same resource blocks to different users and hence increase capacity.

Below is a video explaining their solution in more details:

3GPP Definitions of Small Cells

While the Small Cell Forum defines the different types of Small cells clearly and these Small Cells can be said to contain the complete/partial functionality of the eNodeB, 3GPP definitions of Small Cells can be a bit fuzzy sometimes.

Generally, in the 3GPP documentation, there is a reference to Femtocells and Picocells. Femtocells are Small Cells that are defined as Closed Access (see my old post here) by 3GPP. The open access small cells are referred to as Picocells. Sometimes remote radio heads (RRH's) are also referred to as Small cells, open access type.

Relays, even though not referred to as Small Cells by 3GPP, is also referred to as Small Cells by some people.

Do you know of anything else?

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

LTE C-RAN / Fronthaul Architectures

Its been a while since I talked about C-RAN on this blog. Meanwhile on the 3G4G blog, a presentation by Orange labs have proved to be very popular. Netmanias have posted couple of slideshares on the C-RAN architecture. They are as follows:

The first one is NTT Docomo's advanced C-RAN architecture. I have posted a presentation on Slideshare as well on this topic. It can be viewed here for more details.

The next one is the Fronthaul and Backhaul architecture by SK Telecom. I have a slideshare on a similar topic by SK Telecom here. In fact a post on 3G4G blog from the iGR whitepaper here is an interesting read on this topic as well.

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:

Ericsson's Radio Dot System

Just come back from the SON conference, I noticed that Ericsson's dot system was discussed heavily on what it is and how its different from Alcatel-Lucent Light Radio and NSN's Liquid radio. Here is a bit of detail from the Ericsson press release:

Ericsson Radio Dot System is compact and offers flexible mounting. The device weighs 300 grams, is the result of two years of research and development, and incorporates 14 patents. It introduces a revolutionary antenna element, or "dot," which delivers mobile broadband access to users. Because of its convenient size, scalability, and compelling evolution path, this product caters to different kinds of users in medium to large indoor locations, and aims to address operators' needs of offering a complete indoor solution.

Dots are connected and powered via standard internet LAN cables (Category 5/6/7) to indoor radio units that link to a base station. Radio Dot System leverages the same industry-leading features found in Ericsson's macro base station. Deployments and upgrades are simple, addressing growing capacity and coverage requirements. Thus the users' experience is consistent wherever they go and the indoor network evolves in lockstep with the outdoor network. Ericsson Radio Dot System supports integration with Ericsson's carrier Wi-Fi portfolio enabling features such as real-time traffic steering to ensure the best user experience across both Wi-Fi and 3GPP networks. 

There was a bit more detail available from a discussion in the Linkedin HetNet group here. My edited version of the discussion:

***
A related patent by E///, on how they may be transporting digital I&Q (essentially CPRI) between RadioDot and IRU by introducing APL.

Are we going to see more of Cloud RAN (C-RAN) in future?

China Mobile was in news a few times the last month with regards to Metrocells and C-RAN. The first item from TelecomAsia:

Alcatel-Lucent has unveiled a new TD-LTE metro base station for its lightRadio product line that will be deployed by China Mobile, which co-developed it.

 

The compact lightRadio Metro Radio – revealed at this year’s Mobile World Congress in Barcelona – houses two lightRadio cubes, fully integrated with a directional antenna, with an output of 5W.

 

Alcatel-Lucent says the design allows it to “provide the coverage normally associated with a much bulkier, heavier remote radio unit linked to an external antenna via an RF coaxial cable.”

 

China Mobile will deploy the 2.6 GHz Metro Radio in its TD-LTE network in Shanghai, Nanjing and Qingdao – specifically, in busy indoor and outdoor locations like shopping centers where macro coverage can suffer either from building density or too many people trying to access the network.

 

The Metro Radio is the first product to result from a co-creation agreement signed by Alcatel-Lucent and China Mobile just over a year ago to conduct joint development and test activities on lightRadio TD-LTE projects.

An article on the same topic in Rethink-wireless throws a bit more light:

The TDD lightRadio Metro Radio houses two of ALU's now-famous 'cubes' (highly compact radios which can be installed on lamp posts) integrated with a directional antenna. This enables a level of coverage which would normally require a far larger remote radio unit linked to an external antenna via cable, claimed ALU.

China Mobile's first trial TD-LTE network using the lightRadio product covers 13 cities including Shanghai, Nanjing and Qingdao. The base station will be deployed in busy indoor and outdoor locations, such as retail malls and sports stadia. As well as C-RAN, Mobile also plans to deploy compact metrocells combining 3G, 4G and Wi-Fi on a massive scale in future.

Another one:

ASOCS Ltd., a Silicon IP provider of software defined radio solutions and CMRI, Research Institute of China Mobile (CMCC) Ltd., the world's largest mobile operator, have signed a strategic memorandum of understanding for the joint development, commercialization, testing and deployment of large-scale baseband processing units for China Mobile's next generation Cloud-RAN network.

Earlier trials undertaken by leading mobile operators, identified the bottleneck of Centralized Base-band Units, consisting of general purpose CPU, to perform major baseband calculations in cost and power efficient management. The solution was to introduce significant offloading capabilities of such calculations with highly specialized Modem Processing Units (MPU).

Today there is a growing understanding in the industry that such MPU should support a wide range of system partitioning, topologies and real time system performance, including large scale Collaborative Multi-point communications (COMP) and massive MIMO. Since communication algorithms are evolving over time, and since the C-RAN concept provisions on-the-fly reconfiguration of the BBU to support a variety of mobile communication standards, an MPU solution which is re-configurable at runtime has a great advantage over traditional hard-wired designs.

China Mobile (CMCC) has been pushing the cloud agenda for a long time. A whitepaper from them on the same topic is available here.

Picture source: NTT Docomo press release

NTT Docomo is another operator who believes very much in C-RAN. Occasionally it refers to the C-RAN as Centralized RAN. There were couple of announcements from their side:

The first one was a press release from Docomo here:

NTT DOCOMO, INC., Japan’s leading mobile operator and provider of integrated services centered on mobility, announced today it will begin developing high-capacity base stations built with advanced C-RAN architecture for DOCOMO’s coming next-generation LTE-Advanced (LTE-A) mobile system. The new architecture will enable quick, efficient deployment of base stations, especially in high-traffic areas such as train stations and large commercial facilities, for significantly improved data capacity and throughput.

Advanced C-RAN architecture, a brand new concept proposed by DOCOMO, will enable small “add-on” cells for localized coverage to cooperate with macro cells that provide wider area coverage. This will be achieved with carrier aggregation technology, one of the main LTE-Advanced technologies standardized by the Third Generation Partnership Project (3GPP). The small add-on cells will significantly increase throughput and system capacity while maintaining mobility performance provided by the macro cell.

High-capacity base stations utilizing advanced C-RAN architecture will serve as master base stations both for multiple macro cells covering broad areas and for add-on cells in smaller, high-traffic areas. The base stations will accommodate up to 48 macro and add-on cells at launch and even more later. Carrier aggregation will be supported for cells served by the same base station, enabling the flexible deployment of add-on cells. In addition, maximum downlink throughput will be extendible to 3Gbps, as specified by 3GPP standards.

Another one from Rethink-wireless here:

Japan's Docomo has selected the vendors, Nokia Siemens and Panasonic, which will upgrade its network with certain LTE-A features like carrier aggregation.

This is a good win for NSN, which has not featured as heavily as Ericsson and Alcatel-Lucent in the most advanced LTE roll-outs to date. Breaking into the Japanese carriers is tough, since Docomo in particular tends to rely on trusted local suppliers with which it has long-standing development alliances.

Panasonic, of course, falls into that category - it has worked with the operator since 2007 on LTE network infrastructure, but NSN was also brought into that project at an early stage and its efforts have borne fruit. The European vendor will supply its Liquid Radio multiple standard RAN. Like Docomo's LTE network, there will be heavy use of remote radio heads, with baseband processing virtualized in the cloud, as well as increasing roll-out of small cells to increase indoor and outdoor capacity. NSN says the base stations will deliver capacity of 300Mbps.

In future, the two vendors will support Docomo's own particular definition of Cloud-RAN, a concept which is being pioneered in China, Japan and South Korea, and which takes the idea of remote radio heads and shared basebands to a new level. Docomo says it favors C-RAN because the cell site equipment, consisting of radio and antenna, is compact and low power, and so can be deployed quickly in high traffic areas like train stations. It calls its architecture Advanced C-RAN and this will rely on some HetNet principles, including a separate layer of 'add-on' small cells adding localized capacity while cooperating with macrocells.

In the C-RAN, there will be high capacity master base stations supporting multiple macrocells plus the local small cells. The master BTSs will handle up to 48 macro and small cells at launch and more later. Carrier aggregation will be supported for cells served by the same base station. The carrier says it will boost peak downlink speed to 3Gbps over time, hitting 'true 4G' and 3GPP LTE-B standards.

If you are wondering what 'LTE-B' or the 'true 4G' is, see this post here.

In South Korea, both KT and SK Telecom have announced C-RAN strategies for their LTE deployments, dubbed Cloud Communications Center (CCC) and Smart Cloud Access Network (SCAN) respectively. As early as June 2011, SKT had deployed 1,772 RRHs and 609 baseband units within its LTE network in capital Seoul. The lower amount of baseband units suggests an average of almost three RRHs per baseband unit, assuming each RRH is single sector.

The above two pictures are from the Small Cells Standardization presentation here.

An old article from Rethink-wireless mentions the following:

This is the central concept of C-RAN, deconstructing the traditional base station to leave a low power unit at the cell site, integrating antenna and radio, while centralizing all the baseband activity and supporting hundreds or thousands of sites flexibly from the cloud. KT calls its LTE approach its Cloud Communications Center (CCC) architecture, and it has been co-developed with Samsung and Intel. The latter is leaping on the opportunity to bring its expertise in servers and data centers to the telco network, and in this case its platforms are integrated with Samsung modems to create a centralized exchange for signals communications processing. This is linked by fiber (essential for C-RAN) to the cell sites.

As seen in vendor strategies like ALU's lightRadio and Nokia Siemens' Liquid Radio, the CCC also harnesses virtualization technology so that the central processing resources can be allocated flexibly according to the peaks and troughs of demand in different sites. Yung Kim, senior EVP head of strategy planning at KT, told TelecomAsia: "For example, at a sports stadium you can dynamically allocate more resources for that area during a game on a millisecond basis." The design also improves coverage at the cell edge, he added, claiming twice the capacity per cell, on average, because of better improved edge management.

The CCC architecture can manage 144 base stations per server and accommodate 1,000 servers in each data center, all them acting as a central processing entity. Most tasks are run on off-the-shelf processors rather than dedicated ASICs, also a key trend to reduce the cost of data networks and to converge the norms of the IT data center with those of telecoms. The performance and power advantages of modern computer processors are now up to the task of massive telecoms networks, believe carriers like KT, hence the intense interest of Intel, although some ARM-based chip vendors like Marvell and Freescale are also pushing from the network into the data center.

Do you have an opinion on the C-RAN architectures in the future? If yes, we would like to hear.