Backhauling problems driving up deployment costs?

Going through iDate Digiworld Yearbook 2016, I came across this section on small cells. What caught my attention was the last sentence stating that in Europe, small cells deployments are "being hampered by installation and backhauling problems which are driving up deployment costs".

While this is generally true, there are ways around it when it comes to coverage rather than capacity. When small cells are being used for capacity, there needs to be a high throughput backhaul. Where capacity is the main reason, its generally time and cost which is of essence.

I have talked about how in-band backhaul (IBBH) could be used in case of providing rural coverage and emergency / temporary communications.

I get asked about IBBH many a times. A simple way to explain would be to use the diagram above. If the operator has enough spectrum, the macro layer (frequency f1) can provide backhaul to a small cell that transmits on another frequency (f2). This way there is no interference between macro cells and small cells. In case of in-band backhaul, the small cell would be transmitting at the same frequency (f1). Here, managing interference between macro cell and small cells is the biggest challenge.

Even though I have shown mesh links in the pictures above, its not a must. It just provides flexibility of expanding the coverage further in case the macro connectivity cannot reach other sites.

IBBH is not just a cheap option for backhauling, it also allows very quick deployments. I have seen sites go up within a few hours based on this option. While not perfect, it is a good compromise for extending the coverage.


Related posts and links:

• Small Cells: Best solution for rural coverage?
• Telecoms Infrastructure Blog: Flying Small Cells are here...
• Discrete levels of inband and out of band small cell backhaul - ThinkSmallCell

Rogue One: When Small Cells interfere with Macro

Came across this interesting case study from Cellcom Israel where femtocells cause interference with the macro to reduce availability and in one case paralyze the whole area. Case study embedded below

Multi-vendor LTE Small Cells SON

Before we proceed further, in case the reader is not aware of Self-Organizing Networks (SON), please refer to my old tutorial here.

BT has recently published a white paper on multi-vendor LTE SON based on tests using LTE small cells provided by Node-H and Qucell. From the news posted on Node-H website:

The white paper focuses on the important issue of interference management between small cells. The paper is the result of a joint effort by British Telecom's Research and Innovation group and the technical teams of Qucell and Node-H. It addresses some of the major challenges of LTE HetNets and expands on the work of the 2016 ETSI Plugfest, which was run under the auspices of the Small Cell Forum. The authors’ conclusion is that interoperability between different vendors' SON implementations is achievable and so operators can look forward to robust, seamless and tailored solutions from multiple vendors.

The white paper shows that it is possible to operate mobile networks in which the individual LTE cells execute different ICIC algorithms. These findings challenge preconceptions about SON that are common in the mobile industry and make the case towards larger multi-vendor deployments of LTE small cells and call for bolder efforts in multi-vendor SON testing.

The ICIC algorithms used during these tests have been developed independently and without exchange of technical details between two separate HeNB vendors. Despite this, it has been shown that both algorithms can gracefully co-exist in the same LTE network. ICIC standardization efforts within 3GPP, along with the Small Cell Forum's Plugfest activities, have been key to this success.

The whitepaper embedded as follows and is available to download from here:

Related posts:

• Interoperability and Plugfests for Multi-vendor HetNet's
• X2: The necessity for Interoperability and Interference management in HetNets

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.

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

Small Cells Research Bible

Here is a detailed research on Small Cells from Mehdi Bennis and Walid Saad presented in IEEE Dyspan 2014, this month. Feel free to add any comments for questions you may have.

Recent Advances in Wireless Small Cell Networks from Zahid Ghadialy

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)

Another issue generally faced in case of Hetnets is the Interference management in case of shared carrier. Looks like they may be using a proprietary approach for co-channel deployment and similar approaches are possible with basic SON presence in the network.

Anyway, the complete presentation below:

Building a Sustainable HetNet from Zahid Ghadialy

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:

While I think SON can help in certain situations in case of 3G, the chances of coverage black holes are very high which can lead to radio link failures in ongoing calls. As such, the operator has to be absolutely sure where a small cell will be placed in a shared carrier situation for sake of maintaining a good macro coverage. 

The biggest challenge to Small Cells deployment

Last year when I spoke in the Small Cells Global congress, I listed the small cells deployment challenges as follows:

This list was based on the operator Mindshare session a day earlier.



Small cells deployment is gathering pace and this can be seen being reflected in the recent survey that Light Reading conducted with 103 operators during Mobile World Congress 2013.

The question relevant to Small Cells is as follows:



Its good to see that the operators are concerned about integration with Wi-Fi and Interference challenges.

Complete details of the survey can be found here.