The advice comes after the limitations of mobile network base- station back-up power supplies were exposed during the power outages that affected the North East US in late August.
Mobile telephone operators drew criticism during the power outages when back-up batteries at base stations ran out and networks became overloaded with users making emergency calls.
Unlike the fixed telephone network, which uses a small amount of power transmitted along telephone lines backed up by generators, it is not practical for cell base stations to be backed up by anything other than batteries.
Mobile networks cannot generally cope with the large spikes in usage that can occur during exceptional events such as these.
Arto Vilkman, head of delivery service operations for the US at Nokia, said, "If there is a breakdown in mains power, the base station will turn to back-up batteries. Depending on the configuration of the base station and its power consumption, this could last between two and six hours.
"The capacity of a cellular network depends on the operator's estimation of what level of spending will satisfy customers and meet regulatory requirements. But it is difficult to predict large increases in exceptional circumstances. People behave differently and make more phone calls that last for longer."
Ovum analyst Richard Dineen said the events showed that businesses cannot rely on mobile networks for mission-critical uses.
"If a business depends on a mobile network, it cannot treat the public mobile network in the same way as the public switched telephone network.
"It is generally not advisable to use the cellular network for mission-critical activities, which is why private networks are used by the police and railway companies."