Posts tagged ‘Vendor Voice’

Beyond data offload: Gemalto’s advanced Wi-Fi services put new revenue streams within easy reach

Guest post by Jean-François Gros, Marketing & Business Development Director, Gemalto

Guest post by Jean-François Gros, Marketing & Business Development Director, Gemalto

Among consumers, Wi-Fi is perhaps most commonly associated with the simple pleasures of a few minutes free surfing on the train or alongside a coffee. For mobile network operators, however, the stakes are rather higher. With pressure to build capacity and coverage combining with a fiercely competitive marketplace, the inexorable spread of Wi-Fi offers a compelling route to enhanced customer experience, differentiation, and new revenue streams.

Whilst much attention has focussed on the 4G roll-out, Wi-Fi’s contribution to the connectivity eco-system has largely flown under the radar. But the figures speak for themselves.  It is widely reported that, by 2018, there will be one hotspot for every 20 people on the planet; by 2017, seven billion devices will be Wi-Fi enabled1.

(more…)

Your Data is talking – It’s Time to Listen and Engage!

Guest blog written by Oded Sela, Technical Director EMEA, International Sales at Allot Communications

CSPs are under constant pressure to be proactive all the time, since they need to stay ahead of the competition and are facing challenges on a daily base. But first and foremost, they need to keep their subscribers happy – not an easy task!

What is the secret sauce that they can use for success? Simple: they must analyse and optimise!  Why is analysing so important? Analytics will help operators to find the right optimisation for improving the QoE (Quality of Experience) of their subscribers. It also enables creating and activating optimal use cases, which boosts the bottom line. Furthermore, it allows a CSP to stand out in the crowd, increasing its ARPU and revenues!

(more…)

PCRF: A Vital Component in the Service Provider’s Network

Guest blog written by Udayabhanu Parida, Product Manager, Simulators, Wireless Division, EXFO

Guest blog written by Udayabhanu Parida, Product Manager, Simulators, Wireless Division, EXFO

With the wireless industry moving toward a unified IP network carrying both voice and data traffic, policy and charging rules function (PCRF) will be taking on an increasingly important role in managing the service provider’s network resources and monetization of service usage. And, with the planned adoption of Voice over LTE (VoLTE), PCRF will be playing an increasingly vital role in the network.

A key component of building a fast and reliable wireless network includes extensive testing of the network elements (NEs), in this case PCRF in the test labs before deployment. In test labs, PCRF is normally tested with other real NEs, such as PDN GW. Such a test setup does not fully exercise the functionality, performance or capacity of PCRF, because PCRF not only communicates with single PDN GW, but multiple PDN GWs. PCRF also communicates with policy control enforcement function (PCEF), such as deep-packet-inspection (DPI), online-charging-system (OCS), and offline-charging-system (OFCS) functions, as well as other PCRFs (visited), call session control function (CSCF), serving gateway (SGW), gateway GPRS support node (GGSN), traffic detection function (TDF) and more.

(more…)

NFV: What’s Good? Price/Performance for Starters

Guest post by 6Wind

TL;DR: NFV Promises To Alter The Value Proposition For Network Operators Of All Sizes

As we prepare for SDN Asia 2015 in Singapore this October, we look forward to discussing how executive telecom decision makers want to capitalize on the APAC market’s propensity for rapid technology adoption by providing an abundance of services at the lowest costs. NFV enables rapid service creation while lowering costs, but it is necessary to not sacrifice performance in the process.

Performance continues to drive the NFV discussion because without proper oversight, virtual machines and cloud infrastructure can be real headaches by demanding increasing requirements of hardware to accommodate an increasing software footprint. To achieve an abundance of services at the lowest costs, enabling performance in the initial design architecture will help further drive the costs down. There are two major areas of performance bottlenecks that organizations should evaluate to enable the full promise of NFV.

Drastic Transformation of the Value Chain

(more…)

Carrier Strategies: The Impact of Voice over WiFi (VoWiFi)

This guest post was written by Arvind Rangarajan, Director, Vertical Solutions & Market Offers, Broadsoft

Arvind Rangarajan, Director, Vertical Solutions & Market Offers, Broadsoft

Arvind Rangarajan, Director, Vertical Solutions & Market Offers, Broadsoft

Carrier Challenges

The sheer number of Wi-Fi connected devices is growing at a phenomenal rate, and Wi-Fi is fast becoming the preferred method of connection – at least two thirds of consumers today prefer connecting over Wi-Fi as opposed to cellular, mostly due to cost and performance.

Mobile operators have been increasingly turning to Wi-Fi offloading as a cost-effective way to manage data capacity, and that trend continues. Many analysts are forecasting a steady annual increase in carrier hotspots to more than 7 million by the end of 2015. (Source: ABI Research)

However, data offload is just the tip of the iceberg. The real reason many carriers are out there securing hotspot locations and launching services is competition for new revenue opportunities, from both incumbents and “over-the-top” (OTT) players alike.

(more…)

Bringing Accurate Synchronization to Small Cell Backhaul

This guest post was written by Alon Geva,Timing & Synchronization Expert, CTO Office, RAD Member of the ITU-T SG15/Q13 Sync Standardization Group

This guest post was written by Alon Geva,Timing & Synchronization Expert, CTO Office, RAD & Member of the ITU-T SG15/Q13 Sync Standardization Group

Delivering sub-microsecond time accuracy to the cellular base stations is one of the major challenges facing cellular providers as they deploy their new LTE networks. This is exacerbated by LTE-A’s stringent synchronization requirements and the growing use of small cells in 4G networks, which create unique challenges in the backhaul segment.

Before the debut of 4G, the standard way to deliver a time reference was to install a Global Navigation Satellite System, or GNSS (e.g., GPS) at every cell site. A GNSS receiver is usually referred to as a Primary Reference Time Clock (PRTC). This approach is impractical in 4G, however, given the far greater number of cell sites, the intended indoor location of part of the antennas (e.g. shopping malls), as well as the growing concern about possible jamming and spoofing. Furthermore, considerations of CapEx and OpEx render this approach highly ineffective.

(more…)

Visualise your mobile sites, grow your network

This guest blog was written by Christain Knitterscheidt, Head of Product Management at Tarantula Global

This guest blog was written by Christian Knitterscheidt, Head of Product Management at Tarantula Global

The biggest driving factor for telecom operators is the ever increasing consumer demand for and faster data speeds from their mobile devices. This expansion of mobile usage presents a major growth opportunity to achieve greater revenue for telecom operators. However, this also means finding and securing a variety of sites and installing and managing complex combinations of equipment at these mobile sites.

(more…)

How to get a Net Promoter Score for all your subscribers

This guest blog post was written by Matthew Tworney, Head of Product Marketing, IBM Now Factory, IBM

NPS (Net Promoter Score) as a concept started in 2003. It was developed by Fred Reicheld as part of Bain and Company and Sametrix, and now is a registered trademark. After initial adoption, the main reason why NPS became so important is that it has, in many studies, been directly correlated with business growth. If satisfaction among using services is improved, then revenue grows, which of course makes intuitive sense.

A key difference between Customer Satisfaction (CSAT) indexes and NPS is the way that the questions are phrased. CSAT scores tend to work on questions such as “how do you feel now about the service you just had?” This question is good for judging how satisfaction for services varies over short time periods—think of satisfaction cards in restaurants that people fill out. However, NPS bridges a gap in which NPS looks at how the subscriber feels holistically about the service. This approach is a broader metric to identify those who are happy, those who are thinking of leaving and those who may not do business with you again.

(more…)

Professional testing is key in ensuring high QoE for VoLTE

This guest blog post was written by Kai Ojala, CTO, Anite Network Testing

The requirement for VoLTE is to offer high-quality voice calls and video calls, which as a baseline requires wide LTE coverage. LTE networks fulfill this aspect – especially lower carrier frequencies are deployed globally (e.g. 700 and 800 MHz frequency bands). Operators will benefit from customers switching to VoLTE services by harmonizing voice services and getting better capacity out of the spectrum.
Voice calls in LTE networks can be handled using Circuit Switched Fallback (CSFB) and Voice over LTE (VoLTE). CSFB provides a mechanism to transfer an initiated voice call to legacy circuit-switched networks. VoLTE, on the other hand, is a fully packet switched technology which uses Voice over IP (VoIP) technologies. With the SR-VCC functionality voice calls made with VoLTE can be switched over to legacy networks when the user moves out of the LTE network coverage.
(more…)

Adding Capacity Is a “Small Cell” Matter

Philip Sorrells, Vice president of strategic marketing, Commscope

Philip Sorrells, Vice president of Strategic Marketing, CommScope

This Guest Post was written by Philip Sorrells, VP of Strategic Marketing, CommScope

Everybody’s talking about them, but what exactly is a small cell? In many people’s minds, a small cell is a very low power femto cell, installed in a home or office. It’s a radio device. In my mind (and in many others, too), a small cell is anything that is not a typical macro site, deployed to solve a network capacity problem.

Small cells can be indoor or outdoor. They can vary in power level. Some are carrier grade, some are for consumers. But what defines a small cell is not one of these characteristics, but rather what a small cell is trying to do-add capacity in some manner besides a standard macro site.

(more…)

The Promise of Voice over LTE: Overcoming Today’s Challenges

Femi Adeyemi, PhD LTE Solutions Architect, Fujitsu Network Communications

Femi Adeyemi, PhD
LTE Solutions Architect, Fujitsu Network Communications

This post was written by Dr. Femi Adeyemi, LTE Solutions Architect at Fujitsu Network Communications

 

Voice over LTE (VoLTE) is considered by many to be a revolutionary application, for both mobile operators and their subscribers:  Operators, once they establish VoLTE networks, will no longer have to maintain separate networks—circuit-switched for voice and packet-switched for data. As a result, they will see savings in both operational and capital expenses.  Subscribers who use VoLTE will be able to use high quality voice and data applications simultaneously, while enjoying greater clarity in voice calls.

However, VoLTE deployment has been slower than anticipated due to several challenges…

(more…)

Why do you need a Diameter Routing Agent in a VoLTE deployment? (Part II)

This is Part II of Peter Nas’ Blog Entry: Other DRA added-value in VoLTE

There’s additional value to the fundamental session binding functionality of a DRA. A DRA can enable optimal call management ensuring higher quality-of-service VoLTE calls. For instance, think of all the different vendors’ equipment that is needed to exchange Diameter Gx and Rx signaling. One example is when the LTE PGW has a different Gx implementation than the PCRF. In turn that PCRF can have a different Diameter Rx implementation than the IMS’s P-CSCF node. Typically inside an operator’s network, there will be various vendors for LTE, PCRF and IMS core network elements. And this is the norm in roaming use cases where the visited LTE network is out of control (meaning a different vendor) than the home IMS network, where the P-CSCF (and other elements) will be involved.

(more…)

How can you measure Customer Experience in the Data Tsunami?

This post is by Neil McKinlay, Senior Manager – Product Management, Anritsu

The market is changing rapidly, with new applications and usage models appearing daily. LTE is a major driving force in this change by providing reliable high bandwidth to mobile devices.

The cost of that ubiquitous bandwidth is falling with the realizing of NFV and SDN technology, further pushing down the cost per megabit delivered to the end customer.

This is all great news for the industry, more bandwidth, more users, more apps, new devices, higher quality connections, video support. What’s not to like?

(more…)

LBO or not, I want to break out… (Part II)

This is Part II of Peter Nas’ blog post on local break out technology

 

Peter Nas serves as Senior Solution Architect at F5 Networks and draws from more than 20 years of telecom experience to advise operators how to leverage Diameter signaling solutions to enable the optimal LTE experience. Peter joined F5 with the company’s acquisition of Traffix where he was responsible for global business development.  Prior to joining Traffix, he worked at Tekelec focusing on market development for Diameter and SIP routing. In his days before Tekelec, he served as Core Network Engineering Manager at a prominent mobile operator in the Netherlands.

In my last blog post, I began looking at the slow progress for the deployment of LBO (local breakout) technology that will reduce mobile roaming revenues. In this post, I will suggest various ways to leverage LBO to offset the reduction in roaming revenues.

One interesting aspect of LBO is that the signaling for two additional Diameter interfaces, S9 for policy and Gy for charging, could be exchanged between visited and home networks, and if so, this will be done via an IPX network as per GSMA guidelines (IR.88). There are different views on whether or not using the S9 interface to exchange policy information between the visited PCRF and home PCRF, will be massively used once LBO is offered, but let’s assume it will be used. In this case, an IPX carrier can offer various services around Diameter interworking, security and perhaps also screening, overload control, prioritization and potentially adapting policy rules and more.

(more…)

LBO or not, I want to break out… (Part I)

This post is by Peter Nas, Senior Solution Architect, F5 Networks

Peter Nas, Senior Soltuion Architect, F5 Networks

Peter Nas, Senior Solution Architect, F5 Networks

 

For over ten years, the technology to offer local breakout (commonly known as LBO) has existed, allowing data use by roaming customers to be supported by the visited operator’s network. This is in contrast to the scenario in which data requests are sent back to the roamer’s home network, which of course, results in higher costs. However, despite the obvious fact that many people would like to get lower data roaming rates, a wish not limited to Europeans traveling in the EU, sadly it is not offered yet.

 

(more…)

Operators ‘VoLTE’ over the OTT competition

Marc Bensadoun, CEO of Newfield Wireless

Marc Bensadoun, CEO of Newfield Wireless

This post is by Marc Bensadoun, CEO of Newfield Wireless

“Mobile comms consultancy Northstream reckons European telcos are missing out on over €2 billion in potential profits that could come from effectively partnering with Internet players generally referred to as OTTs,” reported Telecoms.com recently.

Over-the-top (OTT) providers are a big and painful thorn in the side of telcos around the world. Couple this with the growth of 4G and dramatically increased data speeds, and we see how fast the competitive landscape is changing. Now, with Voice over LTE (VoLTE), mobile operators have the power to change it and vault over the competition.

VoLTE gives operators a chance to fight back by providing a native product with the promise of a significantly better user experience. In the process it can solve a lot of operators’ OTT-related challenges. An all-IP technology combines LTE with IMS to efficiently deliver a full suite of services such as IM, video chat, HD voice, presence, and group chat — all opportunities for carriers to differentiate themselves from OTT providers.

In North America, for example, where unlimited voice is the norm, there isn’t as much incentive for subscribers to use OTT voice except for when dialing or traveling internationally. Data or messaging OTT solutions are a different story. However, VoLTE is far from straightforward to deploy and presents operators with a new set of obstacles that are unlike anything they’ve experienced before, especially when it comes to optimising the Radio Access Network (RAN).

Earlier in 2014, several operators delayed their commercial VoLTE launches, citing RAN issues as the cause. The bigger challenge is that VoLTE, and LTE in general, has irreversibly changed subscriber access to mobile services. Engineers that have spent decades perfecting the RAN for traditional voice communications are now faced with the rise of 4G smartphones, all-IP applications and new ways for devices to interact with the core network, which all take time to deploy and test. Given the current transformed network environment, it’s no surprise OTT players have encroached so heavily on voice and messaging revenues – operators haven’t yet been able to fight back, and archaic network testing process is to blame.

With the size and multi-dimensions of today’s mobile networks, legacy solutions like drive testing are incomplete, expensive and time consuming, particularly for deploying products and introducing new devices. New big data-based tools make it simpler and more cost effective to roll out new services. When operators see network and subscriber-level data before a major technology upgrade, they establish a baseline. Big data solutions make this possible. Then, operators can rely on ongoing analytics to see the real-time impact of changes they make to the network, to identify and resolve performance issues as soon as they occur. This is vital for a successful VoLTE launch.

VoLTE deployments are set to double in the next 12 months, according to a September report published by the GSA. The report also indicates engineers are resolving the complexities of managing LTE deployments and are in a position to more effectively compete with OTT players. They need to be. Drive testing alone simply won’t work with VoLTE.

For operators launching VoLTE, subscribers will only be happy if the service is seamless, works well and doesn’t cost them more. Operators need to provide that while focusing on their additional priorities, such as rapid and seamless launch, low operational costs and minimized complexity and challenges associated with deployment. This is essential at launch and on an ongoing basis, as OTT services cannot compete with VoLTE when networks become heavily loaded.

VoLTE is still a young concept, but can be a vital competitive asset. And even though it’s not getting as much attention as bendgate, all new iPhone 6 and iPhone 6-Plus devices come VoLTE-enabled.

It’s only a matter of time before more devices launch with VoLTE, so the time to act is now. Is your network ready for VoLTE?

About the author:  Marc Bensadoun is founder and CEO of Newfield Wireless, a Tektronix Communications company and leader in RAN geoanalytics. For more information, please visit www.newfieldwireless.com.

Five Myths about VoLTE

Manasa Agaram, Product Marketing Manager, Amdocs

Manasa Agaram, Product Marketing Manager, Amdocs

This post is by Manasa Agaram, Product Marketing Manager, Amdocs

Myths give us a nice story, but when it comes to VoLTE, here are five you can disregard.

There is no shortage of industry discussion around voice over LTE (VoLTE).  Some service providers, such as AT&T and Verizon Wireless, have announced launch plans while more are planning trials and proof of concepts this year, as evidenced by our conversations with customers.

Service providers are looking towards VoLTE to provide an innovative and differentiated HD voice experience that will enable them to compete and partner with over-the-top (OTT) alternatives. At Amdocs, we’ve been working with a number of service providers around VoLTE and it’s clear to us that VoLTE is not well understood, in particular when it comes to a fundamental capability such as policy and charging control (PCC).

We’ve uncovered five common myths that service providers need to be mindful of when evaluating their PCC needs for VoLTE. As in any myth, there is often some truth behind it but most often, it’s not the full picture!

Myth #1 – VoLTE is just another use case.

Not exactly. There is tremendous complexity in the set up and tear-down of a VoLTE call, with the right quality of service (QoS) assigned in real time. You will likely have numerous VoLTE-enabled devices on your network. What about the ability to negotiate QoS on a per device basis, based on the device codec’s capability? When it comes to VoLTE trials, there are at least 20 use cases that will need to be tested. (more…)

Putting the pieces in place to make VoLTE work

Eyal Amit, Product Marketing Manager, Amdocs

Eyal Amit, Product Marketing Manager, Amdocs

This post is by Eyal Amit, Product Marketing Manager, Amdocs

There are over 300 LTE deployments around the world, each promising a better, faster and more engaging connected mobile experience. While LTE has brought great advancements with regards to fast data speeds, HD video availability, mobile shopping and gaming, by and large it has not lived up to the hype on voice.

Voice over LTE, or VoLTE should mean conversations in high definition, crystal clear video calls, and easy transitions into text messaging. Consumers should be able to see which of their contacts are available and which aren’t through their contact list, not through a voice message on the other end of the line. Mobile phones were originally designed to facilitate talk, so why have only under seven per cent of all LTE Service providers begun offering VoLTE services to their customers?

(more…)

The Brain behind Voice Quality

Amir Zmora, VP Alliances and Partnerships for AudioCodes.

Amir Zmora, VP Alliances and Partnerships for AudioCodes.

This post is by Amir Zmora, VP Alliances and Partnerships, AudioCodes, and Barry Spielman, head of Analyst Relations, AudioCodes

 Voice quality is a topic anyone dealing with VoIP knows is important and complex. Regardless if your expertise is on the client or server side, if your product is touching the media, you know that this requires constant work as there is always something to improve.

When calls traverse between different types of networks, things can get tricky due to the different network characteristics and the need to mitigate these differences. This issue will be the focus on my presentation at the upcoming LTE Voice Summit in London. I also covered it in detail in my post 3 Things Required for Managing Cross Network Voice Quality.

In this post, I want to talk about the voice enhancement tools available, those tools that would run and be dynamically utilized in the core network element, the “brain” of voice enhancement as I described it in that post.  So I highly recommend that you read that post for the sake of completeness of information.

(more…)

How to simplify the VoLTE routing and control complexity

Pieter Veenstra - NetNumber

Pieter Veenstra, Lead Solution Architect, NetNumber

This post is by Pieter Veenstra, Lead Solution Architect, NetNumber

After a long wait mobile operators worldwide are testing and launching the long expected VoLTE services in their high-speeds LTE data networks now the VoLTE enabled smart phones spread the market in big numbers. With this, customers are finally offered a carrier grade voice app that offers the same comfort and trust to which they have become accustomed to with circuit-switched mobile voice services.

(more…)

Dynamic Multi-Layered Defense – Part II – Why LTE networks are less secure than their 3G predecessors

Leonid Burakovsky Sr. Director, Strategic Solutions for F5 Networks

Leonid Burakovsky Sr. Director, Strategic Solutions for F5 Networks

As I discussed in my first blog, the issue of security for mobile networks, subscribers, devices and applications, is undergoing significant changes with the move to an IP-based technology. In this post, we’ll look at technology trends that are contributing to these new security challenges.

For several reasons, LTE networks are less secure than previous generations. First of all, because they are all-IP networks. The newest security front is between eNodeBs and EPC (evolved packet core). There is no protection there for user information privacy and man-in-the-middle attacks. Only a relatively few mobile operators are deploying IPSec VPN to protect user data and enhance authentication.

(more…)

Off to the LTE Asia Awards: Singapore or Bust

Jim O'Leary, Senior Mobile Solutions Marketing Manager, Cisco

Jim O’Leary, Senior Mobile Solutions Marketing Manager, Cisco

This post is by Jim O’Leary, Senior Mobile Solutions Marketing Manager, Cisco

Think about what is going on in the APJC Mobile Market for a minute:

  • In Korea Mobile data traffic on 2G, 3G, and 4G networks increased approximately 70 per cent between 3Q 2012 and 3Q 2013.
  • In China : Mobile data traffic of China’s top three mobile operators grew 90 per cent in 2012 and 72 per cent from mid-2012 to mid-2013.
  • In Japan, Mobile data traffic grew 92 per cent in 2012 and 66 per cent from 3Q 2012 to 3Q 2013, according to Japan’s Ministry of Internal Affairs and Communications
  • While in India Bharti Airtel reported mobile data traffic growth of 112 per cent between 3Q 2012 and 3Q 2013 and Reliance Communications reported mobile data traffic growth of 116 per cent between 3Q 2012 and 3Q 2013.’Nomophobia’ is a term describing a growing fear in today’s world — the fear of being without a mobile device, or beyond mobile phone contact, which is why analysts report that 91 per cent of us keep their cell phone within three feet of themselves 24/7.cisco-lte-asia-awards

(more…)

Succeeding with LTE in Asia: Go for Next Generation Communication Services

Malcolm Chan, Managing Director BICS Asia-Pacific

Malcolm Chan, Managing Director, BICS, Asia-Pacific

This post is by Malcolm Chan, Managing Director, BICS, Asia-Pacific.

Asia is expected to account for almost half (forty-seven per cent) of all LTE connections by 2017, as LTE networks are rolled out in major markets such as China and India, making Asia-Pacific the world’s largest LTE market in terms of service revenue. In the face of this tremendous growth, operators need to seek innovation through Next Generation Communication Services to maintain market share and customer loyalty.

To achieve this, operators need to ensure they provide an enhanced user experience. Central to this is an enriched communication experience with IMS based services like VoLTE and Rich Communications Services (RCS).

As OTT players increase the number of VoIP and messaging services they offer their customers globally, mobile operators need to deploy VoLTE and RCS services in order to offer innovative high quality services through their unique proposition of ubiquity, global reach, quality and privacy management.

(more…)

De-risking new service provider technology deployments, aka The Triple Challenge of Network Transformation

Andy Huckridge, our Director of Service Provider Solutions

Andy Huckridge, our Director of Service Provider Solutions

This post is by Andy Huckridge, Director of Service Provider Solutions, Gigamon

Operators are facing a slew of new technologies to roll out, but this time around there’s a difference. In the past operators have been able to deploy new technologies in series, that is one after another. With the current new technologies, due to the interdependency on each other, they are linked.

Therefore instead of deploying the new technologies in series, the deployment of one new technology forces the deployment of another new technology, and so on until all three new technologies are deployed. This bog post will explain the three technologies, the interdependencies between them, highlight why this is bad from the operators perspective and explore ways to overcome the resource crunch which will become evident by the deployment of a Unified Tool Rail approach in parallel with the new technology rollouts.

(more…)

Cost Optimised Indoor Coverage

Andrew Mackay, Manager Mobile Solutions, Cisco Systems

Andrew Mackay, Manager Mobile Solutions, Cisco Systems

This post is by Andrew Mackay, Manager Mobile Solutions, Cisco Systems

In my last post Bringing LTE Indoors, I discussed the compelling need to address LTE coverage indoors to enable service migration off 3G, particularly for Voice. We know there is a variety of options for MNOs to address indoor coverage, either from outside in with more outdoor sites, or from inside with wider use of Distributed Antenna Systems (DAS), repeaters or small cells. The “outdoor in” approach would mean even more BTS sites, but site acquisition challenges and build costs generally mean this is no longer an option in urban areas. Addressing coverage from indoors makes sense, but what is the optimal solution?

(more…)

Tag Cloud

%d bloggers like this: