As mentioned before, a tether scheme based on wireless modem consumes additional cellular network resources and many cellular network operators charge a tethering fee for it. Obviously, a tethering scheme free of tethering fee needs to avoid using any additional cellular network resource to what is normally used by applications on a cellphone. It would be a bonus if the tethering scheme makes the traffic from the cellphone into the cellular network totally indistinguishable from regular traffic when not tethered. The latter would discourage cellular network operators from trying to creatively charge things which cost them nothing.
Conceptually, this can be done by making the cellphone into a NAT (Network Address Translation) router. This is just like how your home Internet router works to allow you to connect many computers to the Internet, while your ISP provides you with only a single IP address presumably for a single computer.
The technical difficulty in turning a cellphone into a NAT router for internet connection sharing is due to the lack of accessibility to the TCP/IP stack for modification, which is in the kernel of the cellphone OS. The following is a list of approaches to non-modem tethering.
Yes, you can on most networks. It is your wallet! TetherBridge MIS can help you do just that.
Before you embark on selecting a tethering solution, it is important for you to have some understanding of how it works, not so much as to the technical details but rather to the implications which may have on you as a user. You may want to ask yourself the following questions:
"I am paying for a monthly data plan, why does my carrier charge me for a monthly tethering fee for data usage within my data plan quota?"
If you use the tethering solution provided by your cellular service provider, each time when you connect your laptop to the Internet through your cellphone, a wireless modem tunnel is set up from your cellphone to the Internet gateway through the cellular network. This is in addition to the other tunnel the applications on your cellphone may use when using TCP/IP to connect to the Internet. The same is true for wireless modem solutions provided by cellphone manufactures.
To the cellular service provider, this is not free. It means that they need to set it up (automatically by the switches) each time when you use it and it means that cellular network resources have to be allocated for you, which are limited and could have been used for other customers. At your cellphone end of this tunnel, you get another IP address specifically for your wireless modem connection.
The other twist on tethering charge by carriers is that it is technically feasible and economically viable for the carriers to enforce and to manage charging wireless modem usage because the tunnel setup takes place in the cellular network itself as well, not just on the cellphone.
It allows you to connect your laptop (or other types of devices) to the Internet through your cellphone in a place and at a time where and when your laptop may not be able to connect to the Internet or able to do so economically. It allows you to do many things beyond the limitations of a small cellphone.
Disclaimer:
Discussions of cost and charges made on this site are purely technical and only represent our opinions. Any charge your cellular service provider may levy completely depends on the contract between you and your cellular service provider.
A bona fide tether solution without recurring tethering fees should not incur any significant operational cost, other than data usage, to the cellular network operator, to the tether solution provider, or to you ultimately.
It is unsustainable to use a one-time software license fee to subsidize operational expenses of running servers for supporting tethering. For tethering solution providers which only charge a one-time fee but run tethering servers, the increasing customer base will become a baggage as the time elapses. Eventually, it will reach the tipping point when newly collected one-time license fees can no longer defray the operational cost. The business will then be difficult to continue. If it goes under, customers will be left in the dark.
This is the most technically trivial solution. It allows only those computer applications which are designed with the capability of using port proxy to access Internet through a cellphone turned into a port proxy. Its applicability is extremely limited and its usage is very cumbersome because every instance of usage requires setup work.
When the cellphone OS is allowed to be modified (such as in the Android case), making a cellphone into a NAT router is simple and straightforward. However, for most cellphones including the Blackberries the OS is not allowed to be modified. Even for the open-sourced Android OS, a modified OS may entail voiding of the warranty of the phone. It may also encounter other compatibility issues when installing other applications. The installation itself turns to be more involved. This solution is mostly suitable for only a small group of tech-savvy users.
One way of working around the issue of lacking accessibility to the TCP/IP stack in the OS kernel of the cellphone is to create a NAT router somewhere on the Internet. The only functionality needed on the cellphone is to tunnel TCP/IP traffic between the tethering computer and this external NAT router. This scheme is simple and straightforward as both NAT and tunneling are well understood and have been used in many situations. It does introduce problems of its own however:
How can I tell if my Internet access is through a 3rd-party server?
If the vendor of a tether solution does not even mention if there is a tether server for obvious reasons, it is almost certainly that the solution is server based. You can ask the vendor about this feature. You can also try to determine it yourself. When your PC is connected to the Internet with a tethering solution, you can search "my IP address" from a browser on your PC. Many websites will tell you what your public IP address is. You can then search about this IP address. If you can definitively determine that this IP address does not belong to your cellular service provider, you know your Internet access is through this 3rd-party server with an IP address you found in the earlier "my IP address" search.
Due to the issues with the external server approach mentioned above, we chose not to offer a server based solution. Instead of working around the issue of lacking accessibility to the TCP/IP stack, our approach works directly into the issue head-on. Our solution works within the constraints of a regular cellphone application but yet provides Internet connection sharing capabilities similar to what is provided by a NAT router. You can use any Internet browsers of your choosing, you can use non-http based mail clients, and you can run most other PC applications which use TCP/IP for Internet communication.
This is a bona fide no-fee tethering solution as we do not incur a significant operational expense proportional to the installed base. You can use our tethering solution even in our operational absence. Our approach allows us to remain to be only a solution provider but not a service provider.
