Mobile: The Voice and Data Convergence
Since the mid-1980’s the world’s population has become enamored with conversations over mobile devices. Initially limited to pure voice conversations over licensed and regulated wireless carrier networks, the evolution of smartphones has driven demands to handle data transmission in conjunction with voice conversations. Text chat messaging services have been the primary application employing data but the introduction of the iPhone has demonstrated the potential for leveraging the web onto mobile devices.
The mobile data world is changing with the evolution of (i) the iPhone with its focus on web browsing activities, (ii) the Blackberry 2G-8000 series and 3G-9000 series lines that build out from their widely acclaimed email support and (iii) the Nokia N-series phones as multi-media computers. Combined these three platforms have brought many applications and services normally associated with the wired Internet to the mobile environment; but they need to be adapted and modified to suit the mobile user experience.
Normally wireless communications are associated with the trad/itional GSM or CDMA networks where these terms are associated with voice transmission. On the data side of the transmission we encounter protocols such as:
- GPRS/EDGE on 2.5G GSM networks
- CDMA2000/1xRTT on 2.5G CDMA networks
- HSPA/HSDPA/HSUPA on 3G GSM/UMTS networks
- CDMA2000/1xEV-DO on 3G CDMA networks
3G has become available on most carriers. However, WiFi has emerged as an alternative wireless technology that more efficiently handles data with its main drawback being the requirement to be present at an accessible WiFi access point. On the other hand LTE (4G) wireless protocols are emerging to close this gap with WiFi; but it remains a few years away before carrier deployment.
Handling voice, text and video conversations over wireless presents a variety of new challenges.
Mobile Devices and PC’s — The Fundamental Differences
Skype was introduced at an opportune time in the evolution of the both the personal computer and the Internet.
- Processors were becoming fast enough (> 1.5GHz) to support Skype’s processor intensive activity;
- active memory size was getting up to 2GB;
- 21 inch displays were becoming the norm and
- they had almost unlimited power resources (AC or readily rechargeable batteries).
Skype’s algorithm was based on the founders’ previous experience with file sharing using peer-to-peer (p2p) network algorithms — almost totally eliminating the need for hosted server assets (and the key cost factor in making Skype-to-Skype calling free). At the same time broadband (cable and DSL) Internet connections were becoming the accepted norm worldwide; they provide the data transmission speed required for high quality IP-based voice communications. Security was also an issue which was addressed in Skype’s architecture such that Skype could safely penetrate firewalls and home-based routers without creating spam and virus issues. But it also placed significant demands on the platform’s hardware resources mentioned above.
However, on the mobile device side, even in 2008, we find:
- slower processors (up to 624 MHz),
- lower embedded (RAM/ROM) memory resources,
- physically restricted display sizes and
- limited battery life
In addition wireless technology invokes a balancing act of finding the sweet spot between user requirements and the physics of radio transmission that involves battery life, device performance, spectrum capacity and carrier bandwidth.
On the mobile Internet side it is only with the evolution of 3G networks that we are starting to see a wireless data infrastructure that is capable of handling the volumes of data associated with bandwidth intensive data activity such as video transmission and recording. And in many countries data plans are relatively expensive, although this is changing with the evolution of iPhone distribution. Yet there exists within 3G GSM/UMTS and CDMA services a very robust mobile voice channel that is scalable, reliable, proven and governed by Quality of Service criteria.
As a result, facilitating VoIP-based voice conversations over mobile has been a challenge. As with many other Internet-based applications it needs a new user interface due to the display size but it also comes with significant and expensive demands on both the platform hardware and wireless networks.
VoIP is inherently data intensive — a ten minute conversation can require the exchange of 10 to 20 MB of data; the data infrastructure of mobile networks has been limited due to backhaul requirements of connecting cell towers to the Internet. WiFi and 3G data access technologies are battery draining; the required data processing on the device is inherently slower. Whereas Skype’s main resource requirement is an appropriately configured user’s PC itself, mobile devices simply do not readily lend themselves to the demands of supporting a full VoIP client.
The Mobile Solution: Optimizing the Resources
So what works today:
- Text-based chat and the information to place a phone call can travel over wireless carriers’ data networks with minimal resource and data usage impact
- Voice conversations themselves remain most efficiently handled on the wireless networks’ voice channels.
- WiFi is an efficient wireless protocol for handling Voice over IP, provided there is appropriate support on a wireless device. But this requires physical presence at a WiFi access point.
The best example supporting these criteria are iSkoot’s service for Skype users and Truphone. iSkoot was the original implementer of this architecture (and it led to the evolution of the Skypephone) while Truphone offers a VoIP client for Nokia N-Series devices which works very well over WiFi access points but they went to the above architecture for their Truphone Anywhere service which allows users of Truphone-configured handsets to use the GSM voice channel for the voice conversation.
Skype Implementations on Mobile Devices:
As a result we find Skype access implemented on mobile devices:
- Skype for Windows Mobile: designed for Windows Mobile devices, it works best on WiFi connections; latency issues make its cellphone use realistic only on 3G networks. The main issue here is that Windows Mobile handsets have a rapidly declining market share; Windows Mobile has failed to keep up with competition when it comes to a feature rich smartphone.
- iSkoot: the most prevalent implementation of Skype access via mobile devices. iSkoot clients are available for Blackberry, Nokia N-Series and E-Series smartphones as well as Sony-Ericsson. One advantage of iSkoot is its ability to run over both 2.5G and 3G networks as well as WiFi connections.
- Skypephone was designed as a carrier friendly mobile phone that implements iSkoot in its firmware. Low cost and feature rich have made Skypephone very attractive to a youth demographic in countries served by Hutcheson-Whampoa’s 3 networks.
Accessing Skype from mobile platforms is a challenge due to both device resources (lower processor speeds, limited memory, battery life) and the wireless data protocols that basically do not permit an acceptable quality of voice service. As a result there are services that allow you to access Skype from a mobile device while using the wireless protocol’s inherent voice channel for the actual voice conversation. On the other hand accessing Skype via WiFi access points does allow one to use a full Skype client operating on the mobile device.
One primary consideration for using Skype on mobile devices with respect to entering text: a QWERTY keyboard provides much easier text messaging capability than a “T9” keypad where you have to touch a key multiple times to get most letters.
Accessing Skype via Wireless (GSM or CDMA) Carrier Services:
iSkoot has been the pioneer in implementing an architecture where Skype’s data (chat sessions, presence and call setup information) uses the carrier’s data channel while voice conversations go over the inherent voice channel.
Platforms: RIM Blackberry 8000 Series and Bold, Nokia N- and E-Series, other supported devices . Download iSkoot client here (install via SMS, PC or email request). [links removed]
Wireless access considerations: iSkoot will run across most carriers’ services; simply be aware that an unlimited or high capacity data plan is the major cost consideration. Voice minutes are usually considered as using up your wireless subscription’s local minutes (unless it is a long distance call to one of iSkoot’s many access points worldwide).
The iSkoot software is still in beta mode; does not pass touchtone (DTMF) codes, may require SignOut and SignIn to refresh a session after 24 hours usage.